Thermodynamics are harsh mistress... Add that to limitations on what can be used as refrigerants. The reality that these systems need to operate with rather long duty cycles for decade+ at minimum. And the reality is that there isn't much magic in how they operate. Compression and expansion of gas.

Computers are actually a very special case. They don't really do any physical work in sense other stuff does, thus miniaturization gives lot of gains there. I have long said that small drones are answer to flying cars. We have them and they are small, but lifting people is hard work.