Sounds great. Isn't Robinhood traders the kind of people who just leave funds on the platform though? Not necessarily the people who buy bitcoin and withdraw them to a non-custodial wallet?
Most of Robinhood's customers have their money in cash, stocks, and options. These securities are insured by the SPIC (and FDIC for cash) up to certain limits. I don't think this is the case for any crypto holdings, and it is difficult for most companies to properly insure crypto they hold on behalf of their customers.
Robinhood offering customers the ability to withdraw their crypto is likely part of a strategy for them to increase their userbase.