Erm.. people running away with your sats because it's custodial is the essence of being custodial. That's the tradeoff, you're trusting them.
Why people ever thought getting fiat IOUs from online strangers in return for their perfectly good sats is beyond me.
What did you think would happen?
To say nothing of the part where all the sats just sit on a live wallet on a server.. but then again that's the lightning network as well.