Ignoring the fact that the assumption that you will automatically have as good or better uptime than a cloud provider, I just feel like you just simply aren't being thoughtful enough with the comparison. Like in what world is payroll not as important as your DBMS - if you can't pay people you don't have a business!
If your payroll processor screws up and you can't pay your employees or contractors, that can also affect your bottom line. This isn't a hypothetical - this is a real thing that happened to companies that used Rippling.
If your payroll processor screws up and you end up owing tens of thousands to ex-employees because they didn't accrue vacation days correctly, that can squeeze your business. These are real things I've seen happen.
Despite these real issues that have jammed up businesses before rarely do people suggest moving payroll in-house. Many companies treat Payroll like cloud, with no need for multi-year contracts, Gusto lets you sign up monthly with a credit card and you can easily switch to rippling or paychex.
What I imagine is you are innately aware of how a DBMS can screw up, but not how complex payroll can get. So in your world view payroll is a solved problem to be outsourced, but DBMS is not.
To me, the question isn't whether or not my cloud provider is going to have perfect uptime. The assumption that you will achieve better uptime and operations than cloud is pure hubris; it's certainly possible, but there is nothing inherent about self-hosting that makes it more resilient. The question is your use case differentiated enough where something like RDS doesn't make sense. If it's not, your time is better spent focused on your business - not setting up dead man switches to ensure your database backup cron is running.
> Like in what world is payroll not as important as your DBMS - if you can't pay people you don't have a business!
Most employees, contractors, and vendors are surprisingly forgiving of one-time screw-ups. Hell, even the employees who are most likely to care the most about a safe, reliable paycheck - those who work for the US federal government - weren't paid during the recent shutdown, and not for the first time, and still there wasn't some massive wave of resignations across the civil service. If your payroll processor screws up that badly, you fire them and switch processors.
If your DBMS isn't working, your SaaS isn't working. Your SLA starts getting fucked and your largest customers are using that SLA as reason to stop payments. Your revenue is fucked.
Don't get me wrong, having working payroll is pretty important. But it's not actually critical the way the DBMS is, and if it was, then yeah you'd see more companies run it in-house.