Maybe such requests wouldn't work in consulting/IB/law where it seems like starting comp is very regimented ("our first year asssociates all get $X unless our competitor across town raises their offer to all their first years") or in the case of juniors, where firms aren't expecting much from a 22 year old fresh college grad beyond learn to do things the way we want and grind, but I think there's still value in bringing up such matters even if they are non-negotiable.
"We can't change the contract? Darn, I really care about IP assignment clauses!" gives you some plausible ammo for asking for higher comp without just transparently saying "give me more money because you have it and I want it," plus you're subtly implying you are someone who produces IP that has value, not like all those other programmers who didn't ask.
I've never gotten a company to change their IP assignment clause for me, FWIW, but I have had success getting other exceptions.