I have a "Money Market" account which has an interest rate well above what is laughingly referred to as a "savings account". It was pointed out when I opened said account that there is a six transaction per month limit for this type of account. By transactions I mean withdrawals via ACH transfers or drafts (checks). You are allowed to transfer money into said account as often as you like. I opened this account back in the 80s and I have only hit the limit once, they sent me a letter that said "don't exceed the six withdrawal limit, last warning"!
I inquired as to what gives and they replied that it was a Federal banking regulation intended to cap the amount of interest that a bank could pay on a "checking account". Don't ask why, there are "investment accounts" and "checking accounts" and some federal bean counter has decreed that that's the way it shall be.
You can open "checking accounts" that pay interest but the amount paid is limited to what you'd get in a "savings account", other rules apply like one of your accounts must have "direct deposit" of some fixed amount (payroll or Social Security). Again, only the feds know why...
Regards,
GtG
PS Money laundering regs usually apply to large (>$10K) cash transactions.
These days if you withdraw $3k or more in cash the bank has to notify the IRS.