I'm sorry English is not my mother tongue, does unite mean to syndicate oneself ?

Unite means to join together. You could say you united two pieces of Lego when you snap them together, or when people join in a group it can be called uniting them. The USA is the United States of America because the different states joined together into one nation.

My apologies if there was a misunderstanding over language. Your English is good enough that I had assumed you were a native speaker

Ok that's what I wanted to say. We are all voluntarily united by the same brand of smartphone we buy, why not the same for a healthcare / others benefits groups ?

I gave an example. There could be a franchise of co-working space / hotels / resorts all over the world for nomadic or independent people and they would do the bargaining for their clients.