They are not that fragile if you don't drop hard. Never used case for A50, it still looks almost new after years of active use. But for iphone I got a thin case, to protect popping out cameras and to make it look cool. Main concern is thieves if I travel somewhere, not the physical damage.
Unless you drop them very hard, cases are not needed anymore. Been using a Iphone 12 pro max for 4 years without a case, I don't even look twice and I drop it from the table.