I think it's still somewhat (fairly?) common for internal facing apps where you can just tell your users "It's going to be down in this window, plan accordingly

I think it's still somewhat (fairly?) common for internal facing apps where you can just tell your users "It's going to be down in this window, plan accordingly". For a publicly available app, you'll lose your customers to a competitor with a more advanced maintenance strategy (or even one that happened to pick a NoSQL database where rolling upgrades are trivial)