FOMO DEEZ NUTS!
Seriously though, FOMO exists in any social space and is brought about by the social space itself.
Like why do people care how far they progress with Sortie and Primes? What do they get you outside of faster kills?
It was the same thing in older eras. Byakko's Haidate? Great piece. But a ton of people that wanted them only wanted it, because everyone raved about it. Some people after getting them full timed them as a piece, even when their WS had no DEX mod and were single hit.
But this type of thing isn't just related to powerful pieces. If customization in appearance is a thing, and any one thing gets regarded as the widespread coolest armor piece then...
People get FOMO for style lock/glam items too.
It happens a ***ton in XIV. People complain all the way to the bank about having to buy emotes per character and mounts and outfits, but they do anyway, because they have to compared their modded glammed up *** butt Au Ras to their Oomfies' and feel like they belong.
So XIV does have the same problem, just in another vein. RP and ERP venues? Well, if you don't have MARE mod program in these times, good luck. Want to RP something outside of the current trending character backstory? Well, again, good luck. Last I looked it was privateer.
As outrageous as game systems can become, playerbase driven FOMO is always worse, but the truly bad thing is they often team up with each other for the ultimate crossover event.