Outside a few open source options like zephyr (and FreeRTOS to a lesser extent), RTOSes typically have a worse developer experience than even the shittiest vendor kernel trees. At least Linux doesn't dictate your choice of dev tools like most of the commercial RTOSes do and the libc usually works.
The opposite. Zephyr is one of the more ergonomic RTOSes. Compare that experience to what's offered by VxWorks or Green Hills, which feel like taking a time machine back to the early 2000s in terms of productivity and features.
You’d only do that if you absolutely have to, eg when you’re very constrained by battery or you do actually need real time guarantees. Getting a device with Wi-Fi, BLE, GPS, logging, camera, etc working on a RTOS is just unreasonably complicated when you have a huge battery and 2W power consumption of the SBC is dwarfed by a kilowatt motor.