"If more browsers were still User Agents in the literal sense, maybe we wouldn't have needed this legislation."

s/browsers/popular &/

There are browsers and other clients that are still User-Agents in the literal sense but they are not the popular ones.

The popular browsers measure their success by market share, not qualitative measures.

That is why Firefox tries to stay more or less in lock step with the leading browser on features.

This is not done out of fear of being inferior by some qualitative measure but out of fear of losing market share.