It is more common because that problem is much more widespread and ultimately much more dangerous for the health of the victims.
From a food production standpoint, MSG is a popular additive because it offers an affordable way to enhance the flavor of a wide variety of savory foods. MSG can also be used to reduce the amount of sodium in foods - it contains 30 percent less sodium than table salt, but its flavor-boosting ability keeps low-sodium foods palatable.
All MSG does is add umami flavor, which your body responds favorably to as taste is an indicator of nutrition. So in some way, yes, MSG does make the 'snacks harder to resist', in the same way that literally any flavor makes food harder to resist.
Our body wants sweet/salty/umami/bitter flavors depending on current needs, and naturally gravitates towards foods with those flavors, as taste is a direct indicator of nutritional value.
I think you've made the point: not-very-nutritious food can be dosed with MSG, and then it seems nutritious.
That's what people object to.
MSG is no 'worse' than anything else.
People are stupid when it comes to food. It's probably an evolutionary thing, from back when heeding food lore from other people could mean the difference between life and death.