Yes they are mostly weasel ways of saying No. But humans are strange irrational creatures and for some reason even when you know what the other is doing it's still better to hear I would love to help you but.. phrase.

I've tried the downright No after getting advice it's just better to say No directly, and I can tell you from experience that there is no better way to burn bridges and get people to dislike you when you do that. People seldom respect you for doing that. I think it's some strange disconnect from the theoretical and practical.