Despite their claims of being nothing like the World, their various congregations seem to mirror the local demographics of socioeconomic status. My parents are in a wealthy hall and there is designer purse one-upmanship and vacation home envy. If you can't keep up with the Joneses, well, you'll probably be left out of the social scene.
In other poorer areas, if you advertize your wealth by material means, well, they'll put you in your place by making catty comments and shutting you out of the social scene.
It's because of their strong tendency towards conformity (which they mistakenly thing of as unity). They are like herd animals, anything different is not safe to them. It sends up danger signals in their brains when anyone is different. They must have "unity" to be God's people.