For better or for worse, people like to pump refrigerant through pipes in buildings, and flammability can be a problem. Also this requires a lot of refrigerant.

For better or for worse, people like to pump refrigerant through pipes in buildings, and flammability can be a problem. Also this requires a lot of refrigerant. One can separate the refrigeration part and the moving-heat-around part, though, by using good old H2O in pipes. Water is non-flammable, non-ozone-depleting, cheap, and has zero GWP. It can be a bit messy if a large amount spills indoors, though.