I agree.....IF all you're ever going to do is run a DA. But there's paint guns, air ratchets, blow guns, impacts, and on and on and on and on. A good compressor just makes sense.
It's kinda like NOT having a welder. How would YOU like that? lol
I thought we were talking about sanding on cars only in this thread. For sanding only I don't see where the compressor needs to be involved.
All that other stuff you mentioned...... yes, a good compressor is a mechanic's friend. I do have a badass compressor that could keep up with any DA sander AND another tool at the same time, but I still say, why keep a compressor running with a DA sander when that is redundant.
I found the electric bill is lower using the electric sander too.