I've never used it, but I tried it and it seems incredibly heavy handed. It occurred to me that I might well find a use for it when trying to throw things close to pure black and white in the creation of alpha masks, but annoyingly the adjustment doesn't work on channels.
Pretty sure you can still use ACR on 8 bit jpegs and that's what I'd be inclined to turn to.
I have to admit, the functionality of the adjustment appears to be similar to setting white point, black point and gamma in levels.
Maybe your collegeue has just been doing this a very long time and Exposure is a very old adjustment that was available long before some of the newer tools, so this is their preferred way of working. Personally, I can't think of any useful application for the adjustment right now.