Why is it so hard to create teen savings and checking accounts online?

This was just going to be a rant about Capital One, but this might be a systemic issue.

So a month ago we tried to open a teen savings and checking account for my son at Capital One. Was fairly easy to get the Savings account open and working, but when we tried to create a checking account, the whole thing fell apart. Multiple calls with CS agents, promises to have tech support contact us. I mean, they have all our information since we opened the savings account successfully, why can't someone just help us open the checking account over the phone? They say they legally can't do that. After 3+ weeks of trying to resolve, we finally just closed the account and moved to an online credit union.

Now we're having problem getting the CU account dialed in. You must create an account for the parent, but at them moment our accounts are co-mingled and we can only log in to the parent account.

This feels way harder than it should be. I'm old, when I opened my first bank account, I walked into my local brick and mortar bank and walked out with an account and a savings book.