Yes, but when your script splits money into random amounts and puts things like "pizza money", "rent" and "happy birthday" into the reference field, across thousands of accounts, most of whom also have a real user doing real transactions intermingled, suddenly it gets a lot harder for the bank to filter.
The bank typically has a rather simplistic set of rules to decide to investigate transactions (because they need to be able to explain how the rules work in a meeting with the government whenever their rules miss someone). Things like "Transaction was over $1000 to a new payee or the reference contained the word 'bitcoin'". The investigation will typically involve a human calling the customer, and sometimes asking for more evidence of what the transfer was for - for example, please send us the receipt for the car you said you bought. It's quite an expensive process for the bank.
So, when someone via the API sends tens of thousands of transfers, the bank is spending lots of human hours verifying some/all of those. "My script sent $55 to some stranger because I won a fully automated bet on the weather" is far harder to verify with documentation too. And when some slip through the cracks, they get in trouble with the regulator.
The bank typically has a rather simplistic set of rules to decide to investigate transactions (because they need to be able to explain how the rules work in a meeting with the government whenever their rules miss someone). Things like "Transaction was over $1000 to a new payee or the reference contained the word 'bitcoin'". The investigation will typically involve a human calling the customer, and sometimes asking for more evidence of what the transfer was for - for example, please send us the receipt for the car you said you bought. It's quite an expensive process for the bank.
So, when someone via the API sends tens of thousands of transfers, the bank is spending lots of human hours verifying some/all of those. "My script sent $55 to some stranger because I won a fully automated bet on the weather" is far harder to verify with documentation too. And when some slip through the cracks, they get in trouble with the regulator.