An issue we're dealing with here, unfairly or not, is that the roadblocks to using social stats convincingly in RP are littered with idiots who've done a fairly good job putting the problems we haven't solved in front of the advantages we'd gain from rolling them more frequently.
Idiots trying to strong-arm people into TS? Check. Fools trying to change someone's entire view of the world in one bar scene? Check. Jerks pointlessly brute-forcing social rolls down everyone's throats just because they can? Check.
On top of that we all have our pet peeves. For example mine has to do with politics, and although I probably shouldn't feel that way I can't separate the words on my screen from the intent of the roll which follows them; someone coming to my character with a ludicrous deal ("if you vote for me against your own interests I'm gonna give you this cookie") and lots of dice irks me. And the reason I shouldn't be bothered by it is that the same crappily posed attempt on the physical plane ("I'm'a gonna punch you good!") wouldn't sound half as bad.
I think what'll make a system work isn't incentives. It will however need to give us something we don't currently have - in other words in any social system we care to propose we - the players - must get toys to play with we don't want to be without. Perhaps an overall overhaul of politics wrapped around the use of such attributes with resources, allies and contacts baked into it. But there must be a reason to make players want this in their scenes, and XP ain't it.