> Imagine if cars came in a kit and I could assemble it and choose the fittings myself ... man, that'd be great.

I mean, for a niche certain audience, yes it is great.

But for mass market, people don't necessarily want to take on a whole new hobby in order to experience the thing.

Worse, it's contextual within the same individual: the person who wants to customise the car doesn't want to make their own sourdough pizza from type-00 flour, and customised web browser. And vice versa: each thinks "why waste time on that other thing"?