Even if you only have to buy a plug-n-play harness and insert a coat hanger into a hole to get the old radio out DIYing something like that scares most people and a $50 radio install will probably cost $50 or more before the200% markup on the adapter harness the shop bought on Amazon for $5-$15. Just figuring out how to use typical automotive connectors is a major task for someone who's never done it.
It's a low priority for most people, costs more than you'd think if you don't DIY. OEM radios tend to have pretty good ergonomics anyway.
Most early 2000s and older stuff has a cassette deck anyway so a $3 adapter lets you plug in your phone.
> OEM radios tend to have pretty good ergonomics anyway.
I'm appalled at the UI for radios these days. Obviously feature overload has a lot to do with it; I wish someone would make opinionated car stereos like Apple does for other consumer tech. "You don't want this feature because the tradeoff is more complexity."
If a single DIN radio has a pop-out screen, it isn't constrained any more than a double DIN, and if it doesn't have one, the amount of possible complexity is rather limited.
> ...the amount of possible complexity is rather limited
Relative to what a person can handle while driving, there's far more potential complexity, and as with nearly all things electronic, spec sheets/feature lists often trump common sense limitations.
It's a low priority for most people, costs more than you'd think if you don't DIY. OEM radios tend to have pretty good ergonomics anyway.
Most early 2000s and older stuff has a cassette deck anyway so a $3 adapter lets you plug in your phone.