As a researcher, I often find that my institution doesn't have access to an article I'd like to read. Consider what that means: My own research can't be informed by previous research because of one of these paywalls. It impedes progress, and probably results in a lot of redundant work.
I've said to people that if I were Bill Gates rich and was looking for a good way to spend some money, I'd pay journals in my area of philanthropic interest to go free online. Every one I've suggested the idea too said it was stupid and would make no real difference, I think that it might spur innovation to a significant extent.