The developer, as in people who actually made the games, are usually hardworking & often overworked. However the executives, management could influence resource management. They perhaps think that the user base for X1 one that buy a football games (mainly outside NA where sales of X1 lack far behind PS4) are not significant enough to put in extra effort.
In my experience, PES has very few fans in the US. People here who do like the sport usually buy Fifa. PES doesn't even have a "fake" version of the US league, so you can't easily create the MLS with an option file like you can with European leagues. You would have a tough time finding PES on a store shelf in the US. Anytime I get it, I have to get it online from somewhere.
Also, PES has always seemed to be a PS/PC game. That's where 90% of the good option files are. That just seems to be where most of the community plays. I only remember seeing one good option file for PES on 360.