While crop dusters do not have multiple engines and m/e is not required to fly one, the standard path of becoming a pilot includes multiengine training. I know it sounds silly. It's like wanting to be a doctor without knowing how to spell. I fixated on a particular airplane and job description early on (mine was flying canceled checks) and I thought, why do I need multi and tailwheel to do that. Sure enough, a mile or two later I have them and it has more to do with paying dues than the job. There are lots of things you do in flying to establish credibility that do not have much to do with an actual job. A five thousand dollar Breitling is one of them (kidding).