A poll conducted by GSMArena suggests that Android Auto is used by 50.1% of car owners, while only 17.4% use Apple CarPlay. No insight into the “I use my phone with a holder” camp is given, as they could be Android or iPhone users.
Other poll results are below:
When buying a new car I can see why you would want a system that can handle the phone you have, but I can’t see it being a show stopper. 20y ago I had a Nokia carkit to be reachable in the car. Now I just use the phone for navigation, fitted next to the radio (not on the window, hindering my view). The OEM radio works perfectly ('03 Volvo S80 with entry model, alas also with the entry speakers).
When buying a used car (The cars here are on average 10y old), entertainment is the last checkbox on the list for most (is it there/replacable). With new cars costing at least a year income, they are seldom bought. The business lease market provides the 4y old second hand cars. ;)