I heavily RP all of my characters. We obviously have a different definition of what RPing is. For me that does NOT include eat / sleep / drink. That stuff is just trivial crap, that has no bearing or influence on my gameplay.
For me, it's simple. If it doesn't fit the personality of my character, then don't do it.
And this, OP, is a perfect case in point about how different RP styles can be - and why you should perhaps have thought your post through a little more.
Mr Cinco here doesn't do the whole eat/drink/sleep thing. I do, but we both have perfectly valid (heavy) RP things going on. Equally I fail completely to understand why anyone would want the whole "hey let's settle down and have kids and be suburban Whiterun-ites" thing in a game like this. BUT some people's boats get floated like that.
The point of role-playing is that there is no right or wrong way to do it, it's purely down to whether the individual is comfortable with that.
Sometimes there are synergies between different folk's methods and some peoples' roleplay strikes a chord with others but in the end it's down to each of us who roleplay, to roleplay how we want.
If you don't understand why we do what we do, that's more your problem than ours.
(And given that you state that you roleplay, you should know that already),