A lot of lights have a reputation, but some lights inherit that reputation as a birthright.
This means that people GET a light because it was supposed to be tough, and then when it fails, they consider it to be an exception, rather than representative.
When someone ELSE'S light fails, they consider THAT to be representative, and therefore reinforcing their opinion that THEIR light is tough, and so forth.
I have the same Surefire fans telling me how if their lives depended on a light, they'd want their SF...because they light up "first time/every time"....and at the same time, talking about how often they had them fail and sent back for (free) repairs....
...and they never notice that the light failed them. (It doesn't count)
Same with some other lights.
The fact is that a thick enough body and a good AL, etc....will protect a light regardless of who made it, and most of the lights are using electronics somewhat on par with their prices....and either pot them or don't, etc. Add enough thread overlap and some O-rings, and you have a tough light for the money.
So, the ones that are LESS reliable have less thread overlap, thinner bodies/inferior AL grades, cheaper drivers, no potting, cheaper switches and fewer O-rings, etc.
The ones that check all the boxes are going to be reliable all else being equal.
The ones that skimp are going to be proportionally less reliable, and so forth.
Making a tough light that is ALSO bright, is harder....making a tough light that doesn't need to contain a lot of cells or a large head/lens is a lot easier.
Make the head bigger, and the lens, as well as the rim of the more exposed AL, is proportionally more vulnerable.
Making the body fatter or longer increases the forces that can be applied to it, and makes those forces harder to resist.
The engineering to make a little CR123 powered 120 L light tough is no where as involved as making a TK70 sized light AS TOUGH.
IE: Drop an ant off the cliff, and it doesn't really hit the ground as hard, proportionally, as the dog hits when dropped of the same cliff. The bigger they are, the harder they fall is true for lights too.
So if you make lights small and dim enough to essentially be a small aluminum billet with a light in it, it can be tough as nails. When you need more LIGHT, and therefore need more cells, or larger cells, and a larger head to throw better, and so forth...the light's vulnerability to damage goes up due to the physics involved.
Add more weight for heat sinking materials required to make a higher performance light, and to resist the forces exerted on longer lever arms, etc... and a tough large powerful light becomes too massive to carry after a point.
So, for some people, the small, dim, but hard to break little light works, as they simply don't NEED more light than that...it works for them.
For other people, its just not enough LIGHT, and they need to make compromises to have enough light, and also be ABLE to use it on a practical basis.
That's where the RELATIVE toughness comes into play.
