I love working on cars...I hate obsessing over cars like they're anything more than a utility. Maybe if the upgrades were things that actually improved my day to day experience, but I've never honestly cared about performance specs and my idea of a 'cool' car is one that can fit everything I own into it, play good music, and won't mind if the weather or the roads get bad. Motorcycle upgrades are more fun, but then I care more about the ride on a motorcycle, not the overall utility.
It's the same as computers...I'm not about to trick out a gaming rig from scratch or anything, because frankly I have no use for one and I hate desktops. But I enjoy programming to the extent that it improves my setup (making hotkeys for commonly used functions, like 1 button to rearrange all of my windows into ideal note-taking arrangement while opening OneNote, or a quicker screenshot utility), and if anything breaks I fix it myself.
So I guess you're right...I'm not a car enthusiast. But I'm a big believer in self-sufficiency. I guess I'm more of a DIY enthusiast in general, where it's not the end goal that excites me, but the fact that no matter what it is, I find a way to get there myself. Which also happens to save me money, bonus!!