If your database has a hardware failure then you could loose all sales and customer data since your last backup, plus cost of the down time while you restore. I struggle to think of a business where that is acceptable.
Basic async logical replication in MySQL/MariaDB is extremely easy to set up, literally just a few commands to type.
Ditto for doing failover manually the rare times it is needed. Sure, you'll have a few minutes of downtime until a human can respond to the "db is down" alert and initiates failover, but that's tolerable for many small to medium sized businesses with relatively small databases.
That approach was extremely common ~10-15 years ago, and online businesses didn't have much worse availability than they do today.
The other huge middle ground here is developer competency and meticulousness.
People radically overestimate how competent the average company writing software is.
There's also a big difference between incompetent and inexperienced. Operational incidents are how your team gains experience!
Leaning on managed cloud services can definitely make sense when you're a small startup, but as a company matures and grows, it becomes a crutch -- and an expensive one at that.
I expect most, if not 99%, of all businesses can cope with a hardware failure and the associated downtime while restoring to a different server, judging from the impact of the recent AWS outage and the collective shrug in response. With a proper raid setup, data loss should be quite rare, if more is required a primary + secondary setup with a manual failover isn't hard.
Running mysqldump to a usb disk in the office once a day is pretty cheap.