Any illegal activity requires a financial crime at some point to launder the spoils. Therefore, financial institutions are the perfect place for law enforcement to hook into to try to crack down on the more widespread and organized forms of crime. The financial system is so much of a force multiplier for criminal activity that LE can't really ignore it.
To hook in, they need you to do KYC, they need you to check with OFAC, they need you to do you to do SAR's and report any attempts to structure financial activity. Basically, actors in the financial services industry, as a prereq to being able to do so, have to agree to act as a modern day Stasi.
Thank the criminals and reactionary Congressfolk of the last fifty or so years.
I guess regulation and the technology being fairly hard to iterate on since a lot of systems are running the same software as they were 20-30 years ago when everything was moved over.
I can write checks easily and even manually set up recurring ACH transfers, so why can't I automate that with an API? There are a couple companies that do it, but it's too expensive for doing lots of small transactions, yet it's free through ACH and writing checks...