You have to pay to have that many people on at one time. It is difficult to ensure at least 1 paying person is on for every conversation. We used TokBox until it was shut down.
The vast majority of the users are not going to pay for a subscription of Skype just to get to talk to more than one person at a time when they only get on rarely, or never at all.
Skype just isn't as user friendly as tokbox in that department.