Read this: Why publication in an academic journal matters
It says:
It is through publication that the research, including its scientific and practical contributions, is disseminated to others in a particular field.
Ironically, how can you disseminate research when they put a high paywall right between you and the paper?
And in today's Internet world, can't anyone just publish anywhere?
There are a number of reasons to do so, never mind the existence of self-publishing on the internet.
Some of the reasons are institutional. If you don't publish in reputable journals you probably don't have any future in most of academia. You will be judged, at least in part, and largely in some situations, on your journal/conference output. Some of this is just inertia, of course, but much of it is really valid.
Your answer to another question on this site expressed skepticism of the review process. I think that view was too dim. People, even if unpaid, consider it their professional duty to contribute to the community by making a good faith effort in reviewing. Journals normally use several reviewers for a given paper so that the occasional poor job can be discarded. One person reviews papers so that other people will be willing to review their own papers fairly and honestly. The review process does two things. First it helps authors improve papers even if they are already pretty good. Second, it keeps junk papers out of the mainstream.
So, authors and the community at large get a benefit from the publishing process that wouldn't be in place if everyone just self published.
But there are other reasons as well, some of them going back to fair and independent review. In a world in which there were no gatekeepers on publishing (and there really aren't now - since you can publish on your own) every reader of every paper has to work hard to validate everything that is said. The effect of this varies by field.
In mathematics it is fairly easy to write a paper that doesn't hold up, but "sounds good" due to the use of specialized mathematical symbols and terms (jargon). If I find a paper online, I have to work pretty hard to determine if it has value. If I find it in a good journal, I have some assurance that others, with skills like mine, have already done this and have found it worthy. So my task is eased and I can be more productive myself. Errors occur, of course, so mathematical skeptics are welcome.
In some other fields, especially those relating to health and public policy, a lot of garbage gets published in the "popular" press. The anti-vax community, for example, has caused a lot of harm. Without the vetting process that occurs in reputable publishing, where people independent of the author have an important judgement, the garbage will start to obscure the gems. Enough of that happens already.
And comments on self published work are just about worthless as a judgement. The reader of a bunch of comments has few ways to judge the veracity of the commenter. And bots and trolls are rampant in flooding the space with mis-information on some topics.
A third issue is that if you only publish yourself, then it will be hard to find you. And even harder for people to make a judgement about whether what you say has value or not. An internet search on most topics will turn up a lot of things, of course, but it is, again difficult to sort the treasures from the trash. If I already know and respect some individual, then it is easy to find their work online. But not so easy to find the work of a recent PhD who doesn't yet have a body of respected work (probably in journals and conference proceedings).
Publishing is a public good. It isn't paid for with public money, however. This is both good and bad. Having it be a private undertaking keeps the possibility of governmental interference (censorship) out of the game, but also requires that the money come from other sources: subscriptions, author fees, etc.
So, publishing is an effective and sufficiently efficient (for now) way to make one's work known to a community who might need to see it and may use it to advance the state of the art.
And, for most researchers the "high paywall" doesn't really exist. Many people use grant funds to obtain the materials they need, as well as to pay page fees required by some journals. But even a poor student can obtain free access to nearly everything just by going to a decent library and asking for a copy. You don't even need to go physically anymore. An email to the librarian may be enough if you are an enrolled student. The libraries pay the fees if needed, sometimes using public funds. This avenue may be open to nearly everyone, actually, provided that you have access to a library that, itself, has academic connections.
In my opinion, the link posted by OP gives an overly simplified picture of academic publishing:
Ironically, how can you disseminate research when they put a high paywall right between you and the paper?
Traditionally "dissemination" was meant as "dissemination in the academic world", and it was assumed that academics have access to any publications they want, their institution having subscriptions to any relevant journals. There has been a backlash against this view for various reasons, most notably the fact that research is often funded by taxpayer money but the results are not made available to said taxpayers. Nowadays many funding organizations require that the outcomes of the research are made available through open-access publications.
And in today's Internet world, can't anyone just publish anywhere?
Sure they can (and they do), but without a peer review process there's no evaluation of the quality of the research. That's why there is still a need for reputable selective journals/conferences:
Because a journal validates and collates results. It’s a form of guarantee that the results are probably correct, and it’s usually an entry point to other results in the field. Both aspect add value by minimizing time wasted in searching and collating results by yourself.
You can publish on your own in your own website, but who’s gonna find your papers? And moreover, even if people find your papers, who has the time to read not only yours but the 100s if not 1000s of other manuscripts on a topic by self-published authors?
People bash paywall access - granted I think in some instances they are too high - but it remains that running a good journal takes resources if it is to be done with the level of professionalism that reflect the professionalism of the authors. There are various schemes to get around paywall access, the least expensive of which is to politely ask the author (or another third party) to send you a copy if you don’t have access, or if you can’t find it on the ever expanding repositories.
