I don't really follow boxing at all. I just thought that if a point was to be made against boxing for not making the fight that everyone wants to see, then some comparison would need to be made to the biggest fight everyone wants to see in the UFC also. It's probably not a fair comparison that I made, and I apologise if that's the case, but it's difficult to directly compare boxing with the UFC, given all the different weight classes and organisations.
From my ignorant perspective, I think the reasons holding back both fights from happening are similar and not really related to weight divisions.
The main reason Pacquaio/Mayweather hasn't happened is because both guys are under different promotions, Mayweather is Goldenboy and Pacquiao is Top Rank, it's very different than the UFC which is a league just like the NFL. Because of that the two promotions haven't been able to come to terms on such things as money, venues, and of course the Olympic Style testing which is something Mayweather is extremely adamant about and as a more of a sports fan than a fighting fan I agree with his view of it.
If Pacquiao and Mayweather both fought under a league then the fight would be much, much easier to make. That's one reason why I think the UFC is successful, everyone is in a league and you don't have the under handed promoters like Bob Arum and all the politics involved.