If you have your own servers, it is much much more difficult to deny service, because no one is hosting anything. You are simply asking the provider (Verizon, Comcast, etc) to run a wire to your location. If they deny service it opens up a huge can of worms. This was all worked out a hundred years ago when US government tried to hold Bell Telephone responsible for gangsters using phones to plan crimes.
Thank you. Matze did not sound confident. He did say Parler had “hundreds of servers” so if you don’t have that it would take time to put together.