Probably because their biz plan looks like this:
-Mowing grass is easy, I can do that.
-I can finance a $10k mower for 0% and I'm in business
-I probably can finance a trailer too
-I already have a truck
-@$40-$50 a yard, I can make $350-$400/day plus I can do it for alot cheaper than the other guy so I will underbid everyone and take all the business.
Then the planning stops.
Reality sets in, and they realize how expensive it is to operate and actually see what profits (if any) look like vs the amount of work they done.
Biz and equip goes on CL for less than payoff.
Summer heat also gets 'em and just not realizing how much work is involved in this biz.