Now that I think about it, why would anyone only explore just a few routes ?!! I mean if they play that way then they're missing the full experience aren't they ? It's the same as buying a pizza but you only eat one slice and throw away the rest.... It doesn't make sense.
No matter how good it looks, nor how many times I go to my favorite pizza shop, I'm never gonna get the hot honey slice. It's just not for me. I'm gonna get my favorite slice, and one other thing I want to try.
Same with routes, there's some stuff I just don't want. Ever.
After that its a matter of time and preferences. The game is amazing, but its not the only thing in our lives. I don't have time to play every route, and the things that appeal to me on the first run, I pick. The second run, might be a lot of skipping repeat content, which means I'm not as engaged, so why would i CARE about the next set of characters I 'interface' with?
The only exception is if there are two compelling characters that are mutually exclusive on the same run, thus forcing a redo, but also forcing me engage and care about the second lap.