It depends entirely on how the SLAs are written. We have some that are garbage, and that's fine, because they really aren't essential services, SLAs are mainly a box-checking exercise. But where it counts, our SLAs have teeth. We have to, because we're offering SLAs with teeth to some of our customers.

But that's not something you get "off the shelf", our lawyers negotiate that. You also don't spend that much effort on small contracts, so there's a floor with most vendors for even considering it.