I think Sideshow is hesitant to sell suit sets and Pro bodies seperate, because then their margins are exposed. Sideshow has always been very guarded with their internal policies, but once they start selling suits for $40, and Pro bodies for $30, and people start adding up the costs of the individual components versus the price of a full figure, and then you realize you would've paid $89.99 for Professor Indy, but you can buy a body and suit for $70.
It's the same principle as to why people buy aftermarket parts for their cars. Sure, Toyota makes a good all-around car, but Alpine makes a much better stereo system, so you replace your stock stereo with a better quality component. Sideshow just figures people have already gone to Hot Toys, Saturday Night, whoever, for suits, and they do it better, and it quite simply looks like Sideshow isn't willing to step up. They like baby steps. I always laugh when I see that George Lucas knock-off 'Director' figure and realize that Hot Toys made that figure, know 5 years later, they make incredible piece, and compare that to what Sideshow was doing 5 years ago, and really, there's not that big of a difference.