It works out of the box, is very easy to source (hell some brick & mortar stores sell them), has very good Linux support due to its popularity, and makes up a large part of the install base meaning HA support for it is unlikely to get deprecated.
I was with you until this point. A Pi hasn't been easy to source for almost 4 years now.
Thus the Linux/RaspberryPi underlying complexity is irrelevant to the user - the "complexity" is to dd/BalenaEtcher/etc a downloaded file to an SD card, put the card in the Pi and connect it to power. From there it's available over the network and can be configured through a web browser.