I'm not sure if you know, but canbus is used all over the place, even in aviation. The main selling point is simplicity of wiring and circuitry, as well as the fact that many lower end / cheap microcontrollers have it built in.

Ethernet is great, don't get me wrong... but it is complex to implement in a system like a car. Each device needs to speak ethernet, be switched and likely have an IP stack. If you are lucky enough to have a built in MAC / PHY into your micro (which most don't), then you still need to put in transformers and protection circuits.

10BASE-T1S is the future IMHO, it is much simpler than traditional 10BASE-T, requires only 1 pair and can also provide power. For simple setups, only 2 resistors + 2 caps are necessary to implement and you can have multiple devices on a bus without requiring a switch.

Ethernet is actually older than the CAN bus, even if not by much margin.

Cost, reliability, real-time operation characteristics, and simplicity of wiring (which means less weight and less cost)

I believe manufacturers are starting to switch to automotive Ethernet.

They are including Eth, not switching to it completely. They will keep the CAN buss there as long as it makes sense. Instrument clusters with graphical display output do use the Eth more and more because the amount of data beats the capacity of a CAN bus by far, but devices without big data transfer needs will stay on CAN. For example, what need is ther for Eth for an electronic gear lever? Not much data being exchanged.