Why dont MMA fighter`s turn to boxing?

[Manos de Piedra]

I've tried both and I found boxing more difficult of the two. In my opinion and experience the sweet science is alot more difficult to master than grappling and take downs.

That probably means you are more naturaly gifted at MMA than you are at boxing. Also the level of opposition you fought in either sport.
Its nice to find someone who has done both sports. How did you find the ground game in MMA. Did it come easy to you or did you find people would be able to manouver there way around to always get the advantage. And when you go back into boxing do you find it hard not to try and throw a knee every time you get a fighter that puts his head down to avoid punches.

That might be it, the opposition in boxing was just amateur fighters and in MMA it was beginners to semi pro. I did boxing before MMA so when I started sparring in MMA I found it quite easy to keep guys away with straight punches and front kicks because their stand up was weak. It was easy to block and avoid kicks. For ground game I practiced BJJ which wasn't too bad but against experienced fighters I got maneuvered around but complimented on my strength. The thing is when I was sparring in the MMA gym I would box to keep guy away but when I went boxing I got frustrated and wanted to take guys down. My body shape is more suited to MMA than boxing with my short arms n stocky build.