Because people realized that glaring saturated colors everywhere is garish overkill, and that you don't need to scream personality with every square inch of the objects you own.
We've (thankfully) moved to a world that is primarily more neutral tones, that allow you to selectively choose color accents that are more easily and economically swapped out depending on your mood.
When you're next to a car or getting out of it, it's much nicer for the color accents to be coming from your clothes than from the giant car. That way they highlight you, not a big piece of machinery.
I mean, I'm not exactly advocating for everything to be neon yellow and pink everywhere all the time. I'd just like something to break up the colorless-with-accent (usually something desaturated as well!) monotony that's everywhere, lest the whole world end up looking like Mirror's Edge. It's a balance.
Where the pendulum lies might just be a matter of fashion.
Most cars aren't that interesting so making them invisible with different shades of gray makes sense. Beautiful looking cars deserve nice colors though. I would never buy a gray Porsche.
You speak too confidently about what people realize or want but your advice on how to properly vogue is spot on. You can't take that damn thing to the dance floor, can you? But I don't think it correct to ignore the idea of aesthetic preferences that are not about status or visibility, but rather invigorating and seductive 'things' ;-), the way a properly loved piece of machinery to whom we trust our fragile lives to must and should behave. Sexy. Now that is not about glitz or attention whoring, is it?
Also, I mean, you are right in that over doing anything is likely an error, but Nature is our teacher (so say the same "people") and Nature is rather keen on bright colors. I guess it really comes down on who is doing the splashing around and nothing definitive about saturated colors in themselves.
We've (thankfully) moved to a world that is primarily more neutral tones, that allow you to selectively choose color accents that are more easily and economically swapped out depending on your mood.
When you're next to a car or getting out of it, it's much nicer for the color accents to be coming from your clothes than from the giant car. That way they highlight you, not a big piece of machinery.