Why different servers?

This may’ve already been asked but was wondering if anyone knows why old & new gen players are being kept apart? It’s so annoying that matchmaking doesn’t come up with enough results on the ps4 version. Surely it would’ve made more sense to have old & new gen players on the same server.

Can you do that with other games on PS4/PS3? I know you can’t do it with 360/XB1, even if the game is available for both platforms, but that decision’s on Microsoft not GBX.

(Edited for clarity)

There are crossplay games on the same console family. I know Helldivers PS3/Vita/PS4 can all play together.