Here is what a quarry is to me.
It's a place where I go to meet with my diving friends, hang out, do a little diving, practice some skills and spend a nice afternoon. Yes most of them are on the dark and cold side, but that's why we have thermal protection. If it wasn't for our local mud pit, I'd only get to dive once or twice a year, because of it, I get to dive 20+ dives a year.
As for why quarries, here's my take. First they tend to be deaper and multi-leveled more than lakes and their shear dops make diving better than normal lakes and ponds with gradual slopes to the deeper points. Because they are smaller in surface area, they also tend to not have boat traffic like larger lakes, thus making them safer for divers.