@will13amYes for most people with more advanced smartphones, the PIN doesnt do anything.
In the past where SIM can't found everywhere.. SIM PIN would prevent people from using the SIM card if your phone is lost.. but it is mostly irrelevant now since you can pick up a new SIM and with DIY active / deactivate SIM cards. Also Public is prepaid (also mostly anonymous since there is no identity verification).. so there is limited amount that people who get their hands on your SIM card to do.. (but they don't need your card to do things like SIM jacking, if your Android phone has been compromised).
What the PIN would protect is the personal information store IF the phone does it (mostly in the 90s era phones). They store incoming text, contacts, those could be important but mostly irrelevant in this day and age.