I'm not at all sure that that was the point of the article, and if I felt like being trite I could list a slew of reasons for debate to exist that are mostly independent of how closely the activity mirrors actual or ideal political discourse.

But, for what it's worth, high school debate programs are more properly speech and debate programs. Tournaments do include indirectly-competitive events such as oratory, in which competitors give a ten-minute freeform speech and the rhetorical qualities you seem to value are encouraged and rewarded. Debate is just one aspect of the activity.