players' position change

Did anyone notice that after maybe one or two year, almost every DC will become DC/DM for no reason, and many DM/MC will become DC/DM/MC too, etc.
This feels so awkward and it haunts me.
If this is just several then is ok, but it happens to so many players, the whole world is full of DC/DM now.
Just don't feel right. I tried to edit it but it keeps coming back.

I train DMs to be wing backs or DCs depending on attributes for either flexibility or to improve defensive skills

Never play them there but it just improves quality and in an emergency when theres no more subs they can still drop back and help out as a half back