I think the justification was that it gave us the Junior division, to be honest. If I had to guess, I'd say the rationale was to give Goten and Trunks time to shine and what was the excuse? The tournament. But obviously they wouldn't have a tournament where nobody else enters, so this is what happened. Probably in Toriyama's mind, people really wanted to see Goku vs. Vegeta, down and dirty, and that definitely happened. I would have loved to see Piccolo fighting a Saiyan, but alas, it didn't happen. In this arc, we still got to see Goku, Gohan, Vegeta, Trunks, and Goten in action. So maybe the logic is who cares if they fight against nobodies from the tournament when they can be fighting real threats. Again, the only one I'm disappointed with is Piccolo not having a fight in the entire arc, but that stems way beyond just the tournament itself.
At this stage of the game, where they can punch each other and the shockwave can blow up the entire ring, does it really even make sense to hold a tournament like that? I guess that was the rationale.