Long story short most other boards are not really cheaper if take into assumption that your time is not free.
Unless you enjoy hours of wtfs googling and trying to figure out why does this thing does not do what you want it to, then you are spending a few hours to save a few bucks. You can judge how rational that is based on your hourly rate. Just because RPi is popular it's way more likely that somebody has already solved given problem for you.
So the only argument would be that other boards are more powerful. Does that really matter in 99% of use cases though?
Unless you enjoy hours of wtfs googling and trying to figure out why does this thing does not do what you want it to, then you are spending a few hours to save a few bucks. You can judge how rational that is based on your hourly rate. Just because RPi is popular it's way more likely that somebody has already solved given problem for you.
So the only argument would be that other boards are more powerful. Does that really matter in 99% of use cases though?