18650 cells are internal parts of electronic devices only to be bought and assembled by professional designers and manufacturers. They can't be compared to NiMH, alkaline, etc. batteries sold to general public.
Abuse of such cells in direct consumer applications is common, and acceptable IMHO, because I'm all for "do whatever you want", but there is a problem if people do not know they are abusing a product for a non-intended purpose. This isn't good. You need to do it on purpose, not by accident.
"Protected 18650" is an afterthought concept, and because they are originally designed for a fairly small "hobbyist" segment, the quality varies. The form factor is limiting; it cannot grow in size much, or it won't fit. Because the protection PCB requires access to both electrodes, they must run an unprotected metal strip along the side of the cell. The quality of isolation of this strip varies.
18650 cells do incorporate PTC self-resetting fuses in the cap construction, but power tool cells naturally have higher threshold. A mid-ohmic "almost short", or overload in general, is very problematic because it bypasses such fusing but can still cause damage.