Why did some colonists become skilled craftsman in the middle colonies

Some colonists became skilled craftsmen in the Middle Colonies because it ended up not being enough open farm land for everyone to farm and there was, at that time, not enough of other trades so instead of farming, they went to craftsmanship. Most of the farm land was also covered with a lot of forestry and at the time, tree removal was a very long and lengthy process; this meant that land would open up at a painfully slow pace. Basically, they didn't have much of an option to go to other avenues to make money.

81 is a composite number.