Well honestly, I never read a readme unless I'm having some issues, then the readme is the first place to check.
HOWEVER, when I would plan on actually uploading other people's work as a compilation of addons, I'd check the readme of every single addon to make sure it's allowed. And even if it would be allowed without explicit permission, I'd still drop the original author a note saying I used his addon for a compilation of mine.
It's just common sense to me to do that. Though I do agree with people not reading the readme for general use, I don't when people want to redistribute. It's only common sense to be sure you're allowed to do such a thing first.
Making a separate license.txt won't hurt though, that'll save both you and the lazy compilation authors some trouble in the end.