Four is kind of a personal thing because I tend to have two double tracks a lot of times (for instance bass or a double sampled kick). That way I can tweak the doubled tracks directly while viewing them in relation to another double set of tracks instead of doing it at the buss stage.
So yeah... kind of specific to me but I think there are others who work this way. It's an unfortunate consequence of not always having a great signal due to gear or sample bank limitations. I'm also not the greatest engineer yet so it's easier to blend multiple sounds/tracks to get a full/superior tone than working with one source.
I'm hoping with X4 some of these more luxury features and final interface tweaks get some attention now it's not a game of fixing bugs and oddities.
We really need them to hammer down the last bit of the Take Lane stuff first though like the minimum height, more extensive parent track editing options and adding a Hide Lane type system (I think a Lanes Manager would be great) but that is all woefully off topic. Those are the types of things (as well as some of the suggestions you've been making lately) that would make me upgrade sooner than later because I'm more or less happy with X3e as is.
Cheers.