Oh. Woops. I'm glad you asked. I totally forgot to explain that. I edited the very first paragraph to explain why... But I'll add it here too.

Basically, the primary reason for wanting control over the vents is that in heating mode, by design, the center vents do not operate. When my hands are cold, I can warm one up with the side dash vent, but not the other hand. Turning on the center vent solves this problem. Also, sometimes the heat on my feet is too much. Furthermore, in cooling mode, only the center vents operate, not the footwells. I'd rather just have a switch.