Often times new channels aren't offered to everyone on every cable and satellite service. That channel could only be available to half of the country for the better part of a year. If they can survive that first year or two with half the country not seeing their product, then maybe you have something there.
Also, USA is on basic cable...a huge chunk of the wrestling audience can only afford basic cable. A 24/7 wrestling channel would have to be on one of the higher tiers of cable service, the ones in the $80 and up range.
On the other hand, if Vince signs a deal where his channel is made available to everyone right away, then it's not that big of an issue.