Some clients, especially those less tech-savvy, are reluctant to adopt mobile POS solutions (handhelds).

One reason is they think it looks unprofessional or too "techy" from their guests' point of view.

The other reason has to do with staff behavior at work.
The Bull (hotel in the UK), asked to lock the device so that it can be used only for the POS app, at least by the cashiers. Managers would have a passcode to go outside the app and do other things, but frontline staff needs to access only the POS app.

Android supports this via https://developer.android.com/work/dpc/dedicated-devices/lock-task-mode

Mews Kiosk has this option enabled as well. I think this feature would be interesting and valuable to many clients and would enhance the security aspects as well.