You can blame the war on drugs for that. First Pablo Escobar and other big cartel Columbian king pins killed in the 90s so alot of 100% Columbian Cocaine getting smuggled into the US was shut down. Than we had El Chapo who was another big time cocaine King pin get shut down like 8 years ago. Without big time cartel leaders, like those, there is no-one to run the cartel properly and thus smuggling of cocaine into the US has dropped immensely.

With the amount that does make it here, people are in the cocaine dealing business to make money, so they cut it, the next person cuts it, and than by the time it gets to a common citizen, it's been stepped on to where it's shit.

Also another thing is, more people prefer Meth and Herion over cocaine now a days. So king pins are selling less cocaine and more popular drugs where they can make more money for cheap.