If you don't have the ability to withdraw it, you have crypto IOU's, which is a layer riskier than actually having the assets already.
Robinhood ain't risking much I think. Look at what the ex CEO of Binance got: a personal fine of $50m (while he's believed to be worth about $30 billion), a $4bn fine for Binance and three months in prison (where he'll be the richest inmate in the US).
Meanwhile Binance keeps working.
A federal judge found the SEC has jurisdiction over crypto and is sending Coinbase’s case to a jury trial [1].
[1] https://www.cnbc.com/2024/03/27/sec-scores-big-win-in-lawsui...
Every ruling in the lower courts on these issues will be narrow. The SEC has been on a winning streak recently. The only major kerfuffle was the judge not ruling that XRP is a security, though Torres still ruled in the SEC's favour broadly, and the ruling has been widely criticised (not by industry people, but senior lawyers) for being likely to be overturned on appeal.