Because it's dollars they would not have - there is no point to NOT mining with gear if you already have it.
I suspect even most small-scale miners pull in a lot more than "a couple dollars a day" anyway - that's SINGLE GPU territory in many cases.
Also, why do you ASSUME they don't have a "regular job"?
And to be blunt about it, GPU mining right now is a LOT more profitable on a $/watt basis and in some cases on a $ per dollar INVESTED basis than most ASIC return, with a lot lower risk.
38 cards is what I'd call "medium scale home miner" or "very small scale pro", depending on the specific cards. 18 1080 ti > 38 RX 460....