Biggest reason is business taxes and payroll taxes. They are by far the most racket of everything else. You hear about it on the news all the time. Most start out under the table and can do well but when they get to the big leagues then everything falls apart.
The other big problem is collecting money owned to you. Very very hard my biggest problem. They are so many people that will ask you to cut their grass or even perform a landscape service then will run away. The legal system is set up so the only thing you can do is put your case against their house which now nobody cares because no body is selling their house they are just staying in their big old house pay no bills or mortgage and because of Barack Obama and his policies everybody can do this without being thrown in jail.
As far as all these low baller red necks go. Everybody will blame them for all their problems but in real life they really are not that big of a deal, they will come and go every year and you have to be ready the pick up their work that they leave behind. In my area the hardscaping industry saw this a few years back, everybody wanted to be a hardscaper however it take lots of skill to do it right. When they mess up a job, everything ends up falling apart and then the customer has to pay double for a real hardscaper to fix everything. Same applies to landscaping/ grass cutting.
They will low ball and then
1. Not show up ever or when they want to
2. Smash into the house with the zero-turn or some other object and then run away, because they have no license or insurance their is nothing you can do about it, the legal system allows this to happen, you have to know where they live and a company name and other info to take somebody to court.
After something like this, then they will wise up and go for a professional.