Years ago, banks wouldn't allow you to have more than one savings account. The only way around that was to have either a Christmas or Vacation savings account.
Yeah, that's good ol, Reg D in action.
Regulation D covers the Reserve Requirements for how much money the banks need to keep on their balance sheets, also called Fractional Reserve Banking. The basic premise is this, if someone deposits $100K into a bank account that bank can loan out that money to someone else, that person can then deposit the money into another bank who also loans it out and on it goes. Without a Reserve Requirement, where a bank can loan out 100% of its deposits, that initial $100K becomes $1 Million after 9 loans, but only the initial deposit is "real" money as the rest was simply created through debt. And since banks won't stop at just 9 loans this has the potential to create unlimited sums of money. If that first person was to pull all their money out at once it could cause issues.
Now, if the Reserve Requirement was 50% then that $100K deposit would only allow a $50K loan, then $25K and so on. This slows down the new money creation to where the total is just under $200K after 9 loans instead of a million. When people talk about the government "printing more money" or "tightening the money supply" this regulation is one of the tools they use.
So under Reg D Banks are required to keep a certain percentage of deposits on their balance sheets which means putting restrictions on savings and money market accounts, which are only allowed 6 withdrawals per month. It's also why CDs have lock up periods, to ensure the deposit stays put for a while. Customers could get around some of this by having multiple savings accounts so changes had to be made, like limiting the number of saving accounts. The regulations were changed again during Covid to increase access to money and debt.
Having spent the over 2 decades as a banker I have discovered that around 90%-95% of the stuff people hate about their banks is because of federal regulations. Then people complain to their elected officials, who pass new laws to create more regulations, which causes banks to enact new policies that customers also hate, continuing the cycle.