That is a bit strange especailly for a farmer. Inocculants insure that the plant will fix enough N through its symbiotic relationship with the bateria. Its also, very cheap insurance, I've never heard not to innoculate. Farmers want to innoculate for two reasons, 1. if N is not readily available to the plant it will not yeild to its potential - and this directly effects dairy, or beef production. 2. Most farmer rotate their crops such that following a legume crop, the will plant corn (in my area). The more N thats been added to the soil directly effects their wallet when fertilizing for corn (an expensive proposition).

Dan O and others are right, the plant might still grow even without an innoculant, though usually not as well. In any case, unless the correct bacteria is available in sufficient numbers in the soil, the plant will be starved for N and not live up to its potential.

It could be that farmers that do not use one, may be overseeding, or following a crop that was known to be innoculated with the correct one.