The fees. 0.2% is not low compared to any mature market for trading. As a point of reference, Robinhood is free. Interactive Brokers will charge you a fraction of a cent in commissions, so on a $30 stocks that's about 0.01%
Stock trading is cheap for a variety of factors that's not applicable to crypto (eg. payment for order flow, stock lending [1]). A stock brokerage can also skimp on security because the legacy financial system has an undo button for oopsies. Finally, a 0.2% fee is relatively competitive with a "reasonable" commission of $5-10/trade (the going rate before brokerages became commission-free) as long the trade is below a few thousand dollars.
Why will those factors not be applicable to crypto? (People taking custody of their own cryptoassets may mean that the exchange can't lend them out, but as exchanges continue to pass the test of time more and more people may be willing to leave assets on exchanges.)
AFAIK the only reason why there's a market for lending stocks is because the SEC prohibits naked short-selling. If you want to short-sell, you need to locate a share somewhere and "borrow" it, which leads to brokerages offering to do that for a price. For crypto this isn't required because you can short using CME bitcoin futures, which is cash settled and therefore doesn't require you to locate/borrow anything.
On crypto venues you can spot borrow crypto but there you're right that there is not much demand for this, and as a result lenders don't get paid much.
