It’s pretty simple. They either need federal legislation to say it’s ok for them to be doing this, or it needs to stop being a federal crime, otherwise they are legally required to do exactly what they are doing.
By your right about it being government control stuff, psychological resistance to letting go of the War on Drugs is pretty high, and unless it changes it’s going to remain in the current status quo until enough of them get too old to hold their seats in the House/Senate and new people with less fossilised opinions get to vote on legislation regarding the topic.
[1] https://news.ycombinator.com/item?id=36801491 (FedNow Is Live)
[2] https://www.axios.com/2023/07/20/federal-reserve-fednow-paym...
[3] https://www.congress.gov/bill/117th-congress/house-bill/1996
And very often without any explanations. Sometimes even without releasing acquired funds, like the last street robber (looking at paypal).
Let aside saying that whole industry is drowning in endless useless KYCs, often requiring documents on your grand grand mother, may gods treat her soul well.
I can go on and on, but that's the gist of it.
On a more personal level, I'm not sure why people would use anything other than cash to buy weed... who wants these companies tracking you anyway.
Update: The comments below prompted me to look a bit further into my fraud speculation... quick google search found this:
https://digboston.com/no-more-atms-is-the-smell-of-money-com...
Cash back is a laundering problem.
Wickard v. Filburn (1942) pretty much blew away any limitation on the federal government’s use of the commerce clause. In that case even a farmer’s subsistence crop of wheat for personal use was found to be in violation of a federal wheat quota because such activity in aggregate could hypothetically affect national prices. If that can be regulated as interstate commerce surely all cannabis production and consumption can as well.