I think there are two types of problems:
1. The accidental hiring problems
Suppose I go there and try to hire one or two people for a nice job. Honestly, I don't converse too much because most of the time I get ignored. So I send two requests... nothing. Two more, nothing. Two more, they accept. Meanwhile, persons 1-4 that I requested might have been busy selling crops, busy getting their child a snack or helping them in the bathroom, hiding their screen from their boss for a few minutes... who knows. Then they come back and accept the hire, and all of a sudden there are 6 people harvesting. I never intended to hire so many, I like to give good jobs to people when I can. I have been on the hiring side of this accidental issue, and I imagine there have been times I have been on the hired side of it as well. I am frequently off and on the computer with two homeschoolers here at home.
2. The purposeful hiring problems.
As described by the original poster, some people are just jerks about being hired.
Sorry, I am usually jerky back. If I see:
"HIRRRRREEEE MMMEEE PLXXZZZZZZZZZZZZZZ pineaples !!!"
I hire them... to find my one hidden peach tree.
If I see "Will do a solo job ONLY. Need work. Harvest AND plow ONLY!!!" Then I hire them... and 6 others.
If I can't finish a job for some reason, I let the person know.