3-dash-1 is bound to a contract with their management company. They can only play gigs when their management company deems these gigs are suitable for them and are supposed to get for the band as well.
For the Superband thing, it's the same deal as the rest of these reality-show karaoke competitions they had previously. All the contestants which are voted out are contractually bound NOT to perform in any public places for a year. It's not because they are resting on their laurels after getting 3rd or 4th place in the competition. They'd get sued when they perform without the management company's permission.
Even these winners who get signed on a contract, they are usually entitled to only 6 - 10% of their earnings. Everything goes to the management company which grooms them. This is not just something what a boyband faces. It is something that normal rock bands face as well. Of course, the higher you climb, the more you are able to negotiate with the management company, record label, etc. Of course, it helps to have a good manager which you'll have to pay through a percentage of your earnings as well.
So, welcome to the music industry.
And anyway, even if these boybands can't sing, at least they look good. That, strangely, is a talent in itself. When you play in a band, it doesn't automatically mean you are good to begin with. There are quite a number of bands which are good but the singer can't sing. Isn't that like a boyband situation then? Good backing musicians, crappy singer.