It wouldn't do to catch a whiff of a fellow survivor's drug of choice and eat your week's worth of supplies in an attack of the munchies. Bland, barely acceptable food that you have to really feel hungry to eat makes rationing easier.
tell me about it. i dunno if it's just me, but the sleep aid Ambien seems to have a similar effect on me as pot, complete with munchies. One night i ate all the MRE entrees i had in my BOB/camping pack. I dont' have a local source of MREs, so that pissed me off.
ETA: this site is where I buy my MRE entrees.
http://beprepared.com/quickshoplist.asp_Q_c_E_100_A_name_E_MRE%20(Meals%20Ready%20to%20Eat)