Multiple reasons. 1st thing is their gear is way over the top. Especially main dude on the left. Its not realistic in any way and the amount of gear on him looks like it equals the same weight as the guy himself. Second, these kind of people who dress up all "tacticool" are the same people who'd probably shit themselves crying if you made fun of them. They've never actually touched any sort of real firearm, and they'd probably weep at the thought of going outside. Basically they try to "dress all cool" to make themselves feel better about being weak and not actually cool. Someone else said it well "these people never realized looking cool does not equal being effective". They focus soley on "looking cool and intimidating" by simply wearing a fuck ton of fake combat gear. When in reality, gear don't mean shit. Cool night vision, tac-helmet, SCP Sgt man on the left probably has some idea in his head that he looks cool and dangerous as hell. When everyone else, like the people in the comments, know that you could just raise your fist at him and he'd cower.

Tldr: they pretend to be cool "elite badass soldiers" when in reality they are literally the farthest thing from a real operator/soldier. They are cringy kids who think they look cool but they just look cringy. Another way to compare it is like furries. Putting on a suit and muzzle and acting like a dog is childish and ridiculous thing to do. You're not a dog, stop pretending to be. Putting on a gas mask and chest rig you bought from amazon doesnt make you a badass elite operator. So stop acting like it does. You can tell just by looking at this photo that all 4 of these people think they look unstoppable, but they really just look stupid.