They don't offer any meaningful reimbursement if they lose your data so what does that matter ?
e.g. when Crowdstrike takes down Windows across the worlds or AWS east coast falls over everybody hurts. At that point the story is easy, you point at the broken thing, mumble something about improving resilience, and everyone just moves on.
Roll your own system and have it taken down / breached specifically? There's noone to point at. It's hard to make the narrative anything except it being your fault.