As it seems that switching an old AC system compressors and hoses out to a R134 system is costly, people with smarts looked around, and discovered that only in the North American continent are we restricted by federal laws as to what is in our airconditioning...
But, since we don't pay attention to most federal laws anyway (speeding, magazine capacity, copying movies) why bother wasting a paycheck for a conversion to something you don't want, when some other countries have been using hydrocarbon refrigerants extensively with few to no problems?
Update, Propane works really well as a refrigerant. But, if it ever leaks, you have a bomb. In the early 80s in Mexico, it was a common practice to use propane