The fact that you don't even think of 'farmers' when you think of truck user makes it clear you've got a warped suburban idea of what people use trucks for.
Farmers are a rounding error in the claim "the vast majority of trucks are used for work".
[EDIT] I think, assuming you're posting all this in good faith, it may be a result of expanding a local perspective to the entire country. Some parts of the country definitely do have way fewer non-work trucks driving around, as a proportion of total cars. One might conclude that this is the norm over enough of the country that "the vast majority" of trucks are work trucks. It very much is not.
