From my experience.....
Paintball is pretty much a closed shop when it comes to spectating.
Usually, the people watching are players, their wives/girlfriends, other non participating paintballers but not normally members of the public. The public are free to watch however.
You don't pay to watch, the organisers get their money from players tournie fees, the bigger the tournie, the bigger the fee.
Paintball is getting TV recognition now and with a big tournie at Crystal Palace stadium which Bravo on Sky are televising, then maybe just maybe you might get some public interest.
Personally, I doubt it.
It's down to the organisers really to make it a spectator sport. For example, I was at Mayhem in Brighton this year and the total lack of commentary meant that had I been a member of the public, I would have been totally confused.
Phoenix Paintball used to run good indoor tournies, you always knew who was playing who on what field.
Hope this answers your question.