For me, playing computer games has always been difficult, especially on the immersion side of things. I guess most people with a mind like mine will feel the same, no matter what they're doing. For me to become 'immersed' in anything much is extremely difficult, that goes for everything someone can do in life. I'm actually not entirely sure what being fully immersed in something feels like, unless it's water, then it feels like drowning, and I know what that feels like, unfortunately. -.-
Anyhow, track building, as with all the other forms of 3D modelling I've done, seems to give my acute attention to detail a bit of exercise. Back in the days of ToCA 2 Touring Cars on PSX, I used to get really miffed that these big game producers had messed up bits of the circuits like they had. The first one that springs to mind is Silverstone's Copse and Woodcote corners; I mean come on, they look nothing like that IRL!
So yeah, I strive to create highly realistic looking content, even when creating fantasy objects or scenes. Just because my circuit is a fictional one, doesn't mean I can't make it look totally real, right down to the fire extinguishers on the marshal's posts and the light switches in the garages!
All in all, I guess I must really enjoy racing games, or I wouldn't play them like I do, but I can't say as trackbuilding has made me lose the connection I should have once had with the game. I've always had a very 'odd' connection with games anyway!