To frame it differently, if you want people and businesses to do whatever they want, you need to make sure that the businesses they depend don't become platforms without meaningful competition. But of course the dream of every company is to be so big that they essentially own the market / space.

  > how does the first amendment enshrine [the right of association]

Courts have interpreted “assembly” to include this right.

https://constitution.congress.gov/browse/essay/amdt1-8-1/ALD...