Hello! 
As others have already said above, Windows Store is a very unpopular platform.
- For example, one reason they’re disliked is because they deny you ownership of your own game files for all the games you buy from them, unlike other stores.
- The Windows Store is also full of junk, like very bad mobile game ports, because Windows Store is too relaxed and has no quality control - whereas Steam, Uplay, Epic, etc do.
- Other platforms, like Steam, for example, also has a much larger community, meaning more people to play with.
And so on, I could give you examples why Windows Store is just plain awful all day.
Trainers are only made if the game is popular enough on that platform. Making, maintaining and hosting trainers costs WeMod money, if the game is unpopular then WeMod is not going to get a return for all the effort put into developing the trainer, hence it is what we, in the business world, call uneconomical.
This recent post explains how getting trainers made works and how you can improve its chances: Vampyr for Windows suggestion - #2 by Ravenfyre.