Why is the proportion of self-employed workers more in rural areas?

Majority of people depend on farming 

In the rural areas majority of those depending on farming own plots of land and cultivate independently, the share of self-employed is greater. Most of the people are of the opinion that having your own business is considered under the head of "Self-employed" category. But, in reality all the people who do not work under anyone else are considered to be self-employed be it a vendor or a famer.