If you do, you're a good dealer and probably an outlier. Also, the further you go up the chain of command the less likely you'd be to run into someone accepting these types of payments as well.

I.e. the middleman might let you Zelle him the money, but he is probably paying with physical currency on your behalf to the actual dealer. The dealer might do the same, but the supplier is being paid with physical currency. The dealer supplier allows it, but his suppliers are accepting cash only. Etc.

Meanwhile you can use BTC to have those same drugs shipped to your door, through an onion based marketplace or whatever, or even the clearnet if you arent buying specifically controlled substances.