Because it happens at a low enough frequency that dealing with it at places I've managed physical racks is pretty much a rounding error relative to the hardware costs.

And AWS has other complexities, so the devops costs with AWS are different, but rarely lower than managing physical hardware.

I'd never pick AWS based on total cost - it's an expensive convenience that first starts to pay off in terms of cost once you're big enough to negotiate huge discounts.

If you can afford it, it's great, but a lot of people who use AWS have no idea how much of a premium they pay for it.