First off, great post- I enjoyed the read!
I believe Robinhood does allow you to withdraw your coins, but you have to specifically contact Customer Support and provide additional verification to do so.
I think Robinhood is targeting the demographic that want to dip their feet into the "cryptowaters" at an even earlier stage than Coinbase. Even though you can do the same thing with Coinbase, Robinhood does a pretty good job of simply treating crypto like a volatile stock to the end user in the sense that you can buy it and sell it right alongside Apple or Tesla stock.