Cause a very high % of the population, thinks that item level reflects their skill, and they dont like it when they realize they are part of the cesspool, and not some special snowflake.
Shadowlands has made this more prominent after 2-3 expansions of freebie gear from multiple sources, now that its a bit more limited, all hell is breaking loose.
Because now Little Billy, cant do <insert expansion freebie mechanic like Warfront>/4 dungeon Mythic weekly for HC chest/get lucky with +7-10 weekly chest + random Titanforges for 5-6 months and reach 220 item level when everyone is at 225-230, he is stuck at 210, and now Little Billy is complaining he is not part of the elite, because he doesnt understand how the game actually work.
The funny fact, is the other Little Billy's literally requested these changes