While those are of course valid concerns, I don't think it even enters into the decision making process for most when considering booze vs weed in a state with legal dispensaries. The likelihood of either of these happening in states like CA or WA is just so incredibly low that I don't think either of them is stopping all that many who might consider it today. I think there are far stronger cultural forces at play in terms of why people drink or smoke weed rather than concerns about the above.
You also still can't buy and consume weed in a bar/cafe style setting as you can booze either anywhere in the US AFAIK, which will also play a large part in this. Drinking alcohol can be a social activity in a bar, and of course booze can be bought in supermarkets etc etc.