Indeed, that's what makes the raspberry pi so hard to beat, even though I'm just a hobbyist using it as a tinker toy.

If something major breaks software-wise you can be pretty sure that the rPi community is large enough to produce a fix within hours.

OTOH if you'd like a new kernel for that fancy $65 big.LITTLE 4GB dualchannel ECC Gigabit PCIe SBC then you're at the mercy of your vendor who considers 4.4 LTS ought to be good enough and already reassigned the entire dev team to work on a future hardware release. ¯\_(ツ)_/¯

Plenty of the boards supported by Armbian are on Mainline kernels: https://www.armbian.com/download/