That means there are no orders mishandled either. If no one has an SLA then just switching the servers off without thinking about whether customers were planning on trading seems fully in their right. This is terrible for their reputation, but that does't mean they are going to start handing out money because people argue they could have avoided losses if the servers had been up. It's going to be extremely difficult for any customers to back that up legally.

I doubt that you need an SLA to enforce a penalty for keeping other people's money.

They can probably be fined by some authority, but that penalty isn’t the same as being liable for losses people claim they made because the site was inaccessible. The fine wouldn’t be paid to customers.