Wellp, Fenix, Suefire, Streamlight, etc., that sell to military and paramilitary orgs need to make sure they’re rugged enough for field service. Ie, drop a light, and you don’t want it to bust.
Other lights might not have that ruggedness. No potted drivers or anything. I had a TK4A on my laptop not even fall, but tip over, hit the table, and it croked. Drivers can go mental, whether in software or hardware. Etc.
And everything like threads are well-specified and usually set in stone. Other brands might change from a square thread to trapezoidal or triangular, or might even change the pitch entirely, and even in the same model (early vs late).
UIs are designed to be simple and utterly predictable/repeatable. If you’re using a light, you need to know it’ll do X when you click Y.
In other lights, it’s what people fancy that overclutters the UI, overloads “commands”, varies between versions of the “same” UI, even on the same model light.
Rugged lights are usually locked down, and not mod-friendly. Not to spite people trying to mod them, but to make sure people can’t monkey with them and bust anything, then blame the mfr. Retaining rings might be glued in, left-hand threaded, soldered, etc. Bezels might be press-fit and virtually unremovable without doing some serious damage along the way.
Rugged lights don’t usually bother with aux lights and other blang-blang. They’re there to do a job and that’s it Less to go wrong.
Last, they’re that pricey Because They Can Be. When Uncle Sugar orders lights for the military, etc., they’re not going to pass because the price is too high (think of the infamous $400 toilet-seat). Same with cities/counties ordering for PD/FD. Price is too steep? So? They just soak the taxpayer for more bux. They hardly do comparison-shopping or deal-hunting.
That’s just some of the reasons.
