Basically they come up with new Chumras because they are insecure or are trying to make a name for themselves. It’s not Yiddishkeit at all.
Having said that there are so many cases I see of families that don’t some of them are not Tznius dressed, some of the girls are more dressed for the beach than a simncha, and others are fully covered teens from Beis Yaacov style, in family occassions, so much love in the room at a family simcha, why can’t it be that way for everyone?