Cause it wouldn't fit the story. Pothead's don't lose their temper and inappropriately strike their kids because their high. Not to say that won't happen but then it was because they're an abusive asshole and they'd do it sober too. Weed makes you lazy, not mean. Alcohol can make you mean. Drunks will inappropriately hit their kids when they wouldn't have if they were sober. So she has to be a drunk for that particular plot point to work. Besides no one turns to weed to numb themselves for their ptsd(her trauma being rape of course), they use alcohol.hmm, well, I see... Well, it could be a good improvement. It would be interesting if she smoked weed instead of drinking. I haven't seen moms like that in games yet, but drinking wine is all the time.