The daily/monthly maintenance cycle on a self hosted SQL server is “generally understood” but you still have to wake up, check your security patches, and monitor your redeployments.
You can do some of that in an automated fashion with public security updates for your containers and such. But if monitoring detects an anomaly, it’s YOU, not Heroku who gets paged.
It’s a little like owning a house vs renting. Yes if you rent you have to work around the existing building, and getting small things fixed is a process. But if the pipes explode, you make a phone call and it’s someone else’s problem. You didn’t eliminate your workload, but you shrunk the domain you need to personally be on call for.