They organise events and parties for people who have come into or made a lot of money.
The intent of the party is not to celebrate a birthday or occasion, but rather to get introduced to a new social group of similarly wealthy people.
The service would also construct a guest list and so on for you.
So you wouldn’t need to invite your old social circle, who probably now hate you because you are so rich! LOL ;-)
Yes, this sort of thing does sound utterly grotesque to a generation that can’t find a place to live or afford rent!
But here we are, and if there is money to be made from this, then it’s good that someone is making it! :-)
TLDR; we hate it when our friends become successful.