Actively is the keyword here. Not reclining is the passive, default thing to do, because during takeoff you can't recline your seat anyway. If you had to recline your seat all the way back during takeoff, your argument would be valid.
Most of the time I don't recline my seat at all because I simply forget that it's a thing I can do, especially if the person in front of me doesn't recline his seat enough that I notice it.
