Not all, but many of these MLMs are cults. They intentionally prey on people who are stuck at home, like new moms, some of them, like herbalife targeted churches and church groups. Morons are for some reason a big target. When I was in SoCal, the mormons started to flood in and that was my first real exposure to the insanity that are MLMs.
My anecdotes are not data, but yes, they back up your hunch. There are videos of some of the avon and marykay meetings that look like evangelical sermons. There is a fascinating documentary, Betting on Zero if you can find it is well worth a watch. Another that is really hard to find for some reason is "Selling the American Dream" where they go to some of the 'sales' meetings.
Something like 2% of ALL the people in these programs make money. That's nuts.