Forward & Back

I've been thinking a lot about sweeps from the up/down recently and realized that there aren't very many that exploit balance sideways. The majority of sweeps for an opponent standing above you either take them over you (tomoe nage) or drop them to their back (sickle sweep). There are absolutely some examples of sideways sweeps on a standing opponent, but they're few and far between especially moving into no gi. My opinion is that the structure of the position does not allow for the same sideways kuzushi mechanisms as when both people are standing or one is kneeling in the other's guard. Therefore, because it's more difficult to control the lower body base points, more sweeps function to eliminate them entirely, which leads to more forward/backward, push/pull sweeps. It's very much a theory, but it is interesting to me. What do you think?