Even if its open source, I don't want to spend my own time or depend on other people deciding to keep the software working and building on newer devices just to configure car settings. There's no reason in the world to eschew a touch screen or other control interface in a car and instead put all the control in a phone app.

I would say safety is a big one. It's a lot easier for users to justify fiddling with a touch screen interface when it's a part of the car vs on their phone screen. Sometimes you want to make unsafe things harder to do.

If fiddling with the touch screen while driving is the issue, you can solve that with software lock-outs. The Mazda's touch screen stops responding to touches at faster than 5 MPH, and if necessary you could also lock out option and setting controls entirely while the car is in motion so that even the control knob couldn't be used to fiddle while driving. Moving control out of the already on board computer and control system and onto some external device is just plain over-engineering a worse solution.

The vast majority of these settings are unavailable to even browse on my cars while the car is in motion. No need to go with putting it in a separate app. Which putting it in an app doesn't even prevent it, the driver could still just be messing with their phone anyways.

Even if we achieve that, there are still closed-gardens to open