I use a 90 degree die grinder working on aircraft, there are all kinds of fun little spots you'd never get a full sized grinder into. With the different bits and adapters available I can use it for several different jobs. I use it for stripping, sanding, shaping, cutting, fastener removal, it's easily the most used tool in my box. And being way more compact than anything electric with the same speed and torque is a plus. Using a good 360 swivel air adapter makes getting into tight spots easier, that was always my biggest gripe with air tools, but with adapter it makes life a lot easier.
Sure, it wont slice through a body panel like a 4" electric grinder, but the cuts are more precise, and when dealing with steel body panels, going slower and making less heat would also help prevent warping that you have to deal with when it comes time for the finish and paint.
But that's just me, and I aint no master!
