You can't account for lack of roleplaying in a roleplaying game.I very highly doubt that race makes 0 difference 90% of the time. I highly doubt it's 20% of the time. Maybe your groups just don't try to roleplay.Actually it is. When you design a product, you focus on the most common use case, whatever your customers will want to use 90% of the time. Maybe some of the other stuff is supported, but it's pushed to the back."Most of the time" isn't good enough for a "all of the time" solution.Most of the time, its completely unnecessary to have multiple races in an RPG because player play them all EXACTLY THE SAME. Now, sure there are occasional times where playing a different race may come in handy, like a dwarf being able to be a liaison between the party and a dwarven clan, but that itself doesn't really make it worth it.
The fact is that most of the time players only choose a special race because they want the bonuses that come with it.
Here's why we should have a mechanic for giving each PC cultural diversity instead of racial diversity that all end up being exactly the same: http://stovebanana.wordpress.com/2013/06/05/only-one-race-in-fantasy-rpgs/
In my experience, race comes into play much less than 10% of the time. As in, we all forgot he played a dwarf until he used his dark vision that one time in a 4 hour session. And even that is an ability, not a difference in personality or customs.
That's from about 8 different groups I've played in, and a few I've heard on podcasts or youtube.
The way an RPG is designed could affect how it's played and how much role-playing is encouraged and supported. Just look at the difference between Numenera and D&D 4.