One tangible reason is support costs. A new Mac mini is never going to the Genius Bar because of bad third party memory, or badly seated memory, or a static shock administered to the mother board while the memory was being changed.
Even if those are quite rare, support incidents can be expensive, so it could be a dollar or two average per mini being saved.
I remember when CMOS was new and static really did damage just about every part you handled if you weren't careful. Little conductive wrist band connected to steel desk, carbon coated conductive foam to work on and so on. But for the life of me I can't remember when a part failed due to static in the last decade or even longer. If anything broke it was either a cable or a soldered connection to a board.
Sure, I've had RAM break, but that was factory installed RAM that was several years old. This is definitely anecdata but it would be interesting to know how much damage static really does these days. If you're going out of your way to pet your cat prior to installing your RAM chips on a glass floor or something like that then you're probably asking for it. But regular precautions (place RAM container on the case before opening package, hold the case while inserting the RAM) seem to be more than enough. On chip ESD protection has come a long way since the 80's.
Even if those are quite rare, support incidents can be expensive, so it could be a dollar or two average per mini being saved.