not really, but imagine that you're a drinker that also smokes pot occasionally. what do you do when alcohol no longer gives you any satisfaction? increase the consumption of the other, or if you're not using smth else, look for other stimulants or disinhibitors. it's not about gateway drugs, it's about addiction swapping!

Edit: + and it's not like if you're a pot smoker, you're gonna start doing heroin when pot is no longer enough for you, so I don't believe in gateway drugs.

I don't think there's necessarily an implication of the validity of "gateway drugs" there. The same idea crossed my mind, but only if this sort of treatment is not accompanied by anything else.

It's generally agreed that people abuse alcohol because of some sort of underlying problem. If you take the option of alcohol away and do nothing to address the problem, then it's reasonable to assume that they will look elsewhere.