I mean yes it's true that JP Morgan isn't going to go bankrupt if they cash some bad checks but at the end of the day that's money that could go to opening new branches, hiring employees, paying bonuses or depositors more interest. The cost to society is the same it's just distributed over a larger number of people.

I bet more than one corner shop worker had money in FTX.

Sure. If you put your money slightly outside regulated banks, you implicitly accept the risk of losing it.