I once played FIFA on the Xbox, but there was little trading because there were only 1,000,000 active transfer offers. The same problem exists on the PC, because FIFA is a typical console game. On the PS4 there are 7-10 million in comparison. Active transfer offers.
But why doesn't EA do crossplay, that's standard nowadays. Games like Fortnite have presented, Rocket League and Warzone have followed suit, but EA is sticking to it. I and many others would get the game if there was crossplay, because not everyone wants to spend 100 euro / year on PS4 plus or Xbox One Plus.
Crossplay itself has nothing to do with the cost of online games?
The reason is very simple: for Playstation (Sony) it is an advantage, as it is an argument for the PS.
I don't know why this is the case, nobody will know, but can only puzzles. The only thing that comes to mind is that the console market and PC market were always different (in the game itself) and cheats.
It's not that EA doesn't want crossplay, there are some EA games that have the system but just not with FIFA. Maybe because FIFA is a huge source of income because people are buying these items like crazy. With a PC, you can somehow manipulate the system like so many other things.
It could also have something to do with cheats. In CoD Warzone you can see that console players like to switch off crossplay so they don't have PC cheaters.