I think that's extremely dangerous and I would never consider this to be honest. My phone is my only phone, and I need to be able to call emergency services, or answer an important call, at unexpected times.
If I reached the point where I was comfortable literally being unable to use my phone for a period of time, I would just not have a phone or not carry it with me.
You literally can do both without entering your unlock code. That is the whole point, locked phones are pretty useful, but not to kill time.
You can even do more like make outgoing calls using Siri/Google Assistant, Take Photos/videos etc. This is default setting at least on iOS.