I do know what you mean, in the race proper I'm looking at the road and not the pretty details on someone elses machine. But I tend to watch the replays back and enjoy making videos and things so I see more than you otherwise would, and for me there's an immersive quality to the whole thing. Especially in the FIA events when at the start you get a look at the entire grid etc. so I appreciate it when someone has taken the time to put their original stamp on what they are driving (or take the time to download someone elses!) rather than using the same stock livery.
It feels more realistic. I've never been to or watched a racing event where every car looked the same, even if its a one make event/championship.
Having said that, at least the stock liveries for most of the cars are actual proper liveries. What I really hate is when a car doesn't actually race in the relative Group and so it gets a slap dash splattering of colour with no attention to detail. Or indeed when you get a certain Italian Super Car Manufacturer enter the scene and you're lucky to actually get a car full stop, let a lone a licensed colour scheme to boot.
I guess what I'm trying to say is if you're the kind of person who pootles around in a stock red Gr.3 458, we can't be friends...