You do know most lithium ion cells fails physically, and not electrically? A protected cell would not help in this case, at all.
And this is why reviewers exist. I wouldn’t buy an old Convoy C8 to a friend, since I checked with a power supply that it doesn’t include LVP. Many reviewers here test lights so the consumer can make a good choice, and LVP is the one thing I always take into consideration.
And besides, an 18650 will never fail catastrophically if you discharge it too low, and then charge it back up. A good quality charger, like from companies like Liitokala, Nitecore, XTAR, Efest, etc, will handle that well. The 18650 will just lose a bit of its cycle life down to 80% capacity.
And most flashlights don’t pull a ton of current from the cells, have LVP and reverse polarity protection, and have thermal protection/don’t get too hot.
And besides, if LVP fails, the light usually fails to turn on, since it’s part of the IC.
It’s the opposite for a protected cell: the protection circuit can short out, or be destroyed and keep the circuit open. I’ve actually had one from Imalent that suffered, by my mistake, a direct short. It grilled the IC, and put the cell worked thankfully.
I then tried to discharge it down below 2,5V, and surprise!, it continued working down to 2,0V.
TLDR: Get quality stuff that was reviewed, use a quality charger from a mainstream “enthusiast” brand, quality TESTED cell, etc.
Knowledge is power.