MR16 is a 12V DC standard so it does not need a transformer, in theory it's much better for LEDs, and yet we hardly ever see it used even in new builds.
Every time I rented a place with MR16, like 1/3 of all sockets in the ceiling were dead, the power supply was inside the false ceiling and it was not possible to fix without making a hole. Needless to say lardlord need much motivating to fix anything.
Also, it;s not illegal to install random non-standard bulbs -> my last apartmentblock was built with some special, great, proprietary and patented LED-spesific socket. Guess what happened? 15 years on, the lamps started failing, and the manufacturere dropped production of anything for that socket!
Now they need to replace like a thousands light fittings across the entire block, there is no way to get replacements. Some of them are in awkward places and will require a special vehicle to reach.