With most pre-written SLAs, the penalty is something like "we'll refund the service cost for the month" at best. So it's "we have a financial reason not to fuck up" not "you will be made whole if we fuck up and your business is down".

The SLAs are also often tied to SLOs (the quality they promise to deliver, e.g. "we promise to be up 99.5% of the time") that are very generous for the service provider. If your critical service was down 3.6 hours in a month, that would still meet a 99.5% SLO. So if your business was down for 2-3 hours per month, that would be a-ok. Only if it was down for say an entire day, you'd get (depending on the contract) typically either a day or a month of service refunded.

I'd take a provider with no SLO but a good track record over someone that offers an SLA. If they fuck up the month of refund is going to be the least of my problems, and if they fuck up repeatedly, I'll have to emergency-migrate away to a different provider either way.