It all comes down to money. Yes, they could buy a new Cub Cadet XT3 GSX but most people are too cheap to spend $6100 on a tractor and probably another $1k for a deck. Deere makes some nice machines too but the X500's start out around $7k and the X700 series start out around $12k.
I have 2 friends that purchased POS throw-away riders at Home Depot 12 years ago. One was a little over $1k(Toro) and the other was about $1,700(Deere). Both guys are still running them today but I will say that they have small yards (3/4 acre) and only mow with them.
That's my story and I'm sticking to it!