If they're intentionally causing the customer to have an unspendable balance, knowing that it's making them $200m/yr, how is that not fraud (or some kind of crime)? I'd expect atleast CA would do something about it.
Expecting people to read those for most simple sign ups is already a high baseline, and Starbucks is not technically a banks and offers no consumer protections (FSCS or other), so that feels knowingly misleading, even if the total balances held are small per customer.
IANAL, of course.