If it’s in a contract, companies can sue. And big enough customers who have lost enough money due to the outage would definitely threaten to sue to recover that money.
We just ask nicely. Never really had a problem getting a huge % discount on the bill because of an outage. Extra bonus for us since there's no bottom line impact since we can tolerate some downtime (just annoying for engineering).
Wouldn't the contract specify the remedy? Or do they actually on paper really promise uptimes that on a single isolated data-center level no one can keep?