The why reason...

It's been mentioned already...

Independence:

No one can sack me.
No one can hold me back.
No one can muscle in on my territory.
I have no crops to fail.
The government can't do anything but ask for my tax share.
The weather can't screw my business but for a small time. (communications , power maybe) ....hell, just relocate if it does.
The economy hitting recession won't be worth worrying about. As long as somethings changing value, I can make money.
Technology won't steal my wage.
I can take time off whenever I want.
If someone elses screw-up, it can't destroy what im doing.
As time goes on, my earnings will increase.

...many more reasons for sure.

As long as there is a market and access to it, I'll have a source of income.

And the better I get at this, the more enjoyment I get from it.