Earlier quoted context omitted.
Question is, why don't scientists just put everything on public platforms (read: github) and call it a day? Is it only a matter of funding, or do other factors also play a role in that?
For all its faults, peer-review is still the best mechanism to keep science in right track. What you propose would mean twitter or facebook will replace those journals, people with huge twitter followings, or "celebrity" scientists would dominate science, the works of people without such marketing skills would get drowned out. (This is sort of true for current system too, but I think situation would be much worse in…
Isn't that at its core the same as with scientific journals? People trust these journals to curate science in the same way you suggest twitter would come to curate science if it made the move online.
1. It's already possible to call attention to a paper through twitter, regardless of whether it's published in a journal or not. Paywalls gate-keep the content somewhat and makes sharing easier, but that's a minor side effect of a very broken system.
2. Papers (and involved data) being available on public platforms like github that already have mechanisms for reporting and tracking issues as well as built-in review tools, in githubs case even a separate discussion feature now, would allow for much quicker discussion critizising bad methodology.
3. Working with a VCS like git would automatically make it clear who wrote, edited or removed what.