Why Vote For A Free Lunch?

When I was 7, my grandfather told me, "There ain't no such thing as a free lunch."  He explained that whoever was offering "free" stuff always had a hook in there somewhere that would probably cost you as much or more than a paid lunch.  I idolized my grandfather, so I paid very close attention.  His explanation made perfect sense, both at age 7 and ever since.  What I will never understand is how adults in massive numbers will vote for politicians offering free stuff, and not even consider there might be a hook in there somewhere.