Recirculate question

I'm just curious why my '10 Frontier disables the recirculate air feature when the controls are set to anything other than face vents only or face/floor. I will usually throw recirculate on when I'm driving past something smelly such as a dump, etc - but in the winter time when I'm most likely going to have the controls on feet only, you cant use recirculate until you switch it to feet/face (or face only).

Just curious what they were thinking with this.


Thanks,
Rick