As a rule of thumb flashlights only have LED driver in them and lack any sort of battery protection.
This hasn't been true for a quite a while. Most Li-ion flashlights have a low-voltage shutoff.
Most 18650 batteries that you buy from reputable sources have built-in protection circuits.
Also not really true. Top-tier dealers like Illumn and Nkon offer both protected and unprotected options. Some popular flashlights (Zebralight, Emisar/Noctigon) only accept unprotected cells.
even most lithium cell chargers rely on the cell having built-in protection circuit.
No charger anybody should be using relies on that. Correctly charging Li-ion requires tapering current after reaching the target voltage, which can't happen if it trips a circuit breaker.