There's an opportunity for mobile OSs to support this usecase with a "guest" account: lock the phone to a single app so you can hand it to a less trusted person. Also useful for toddlers gaming.
The last Android version had a weak guest mode; the current one does not seem to.
Not quite a guest account, but you can use the Accessibility shortcut (from the Control Center or triple-clicking the sleep button) to quickly prevent app switching before handing a device to someone.
You can even use it to disable interaction with parts of the screen by drawing regions, or disable the hardware buttons, and set an autosleep timer.
What operating systems really need though, is a "fake OS" mode. It should display an alternative launchpad with some random apps with random photos, notes, messages etc. When someone tries to do something it should stall with poor network connectivity dialogs or other fake issues.
The book Little Brother by Cory Doctorow mentions an innocuous home screen or desktop that is accessed via alternate password and I've always wanted to see it actually implemented.
There's an opportunity for Apple to integrate it with Wallet, as they did for the Japanese public transport tickets. You can bring up cards from wallet without unlocking your iPhone.
The last Android version had a weak guest mode; the current one does not seem to.