Economy-size mouthwash

Why is there economy-size mouthwash? Since it is antibacterial, couldn't you just reuse it? And if your problem is viral, you had it in your mouth anyway, so what's the big deal? I figure you just need to have one travel-size thing of mouthwash, and you can just reuse that until it stops smelling the way you want your breath to smell, which I figure to be at least as long as the big size would have lasted at your current rate of use, or close anyway.

My apartmentmate mentions that one could do the same thing with chewing tobacco, if one drinks heavily at the same time for the antiseptic effect.

Backlog Bob