Apple will use it's dominant position to create lock in like how they did with iMessage instead of cooperating with other platforms on a common standard.
Oder friends and family are surprised when they want to video call over Facetime and find it hard to believe other people's phones don't have Apple apps.
The telcos specify the size limits of MMS messages. iMessage has much higher limits in most cases, so iPhone has to use reduce the quality of the pics/videos to reach the lower size limits for sending to non-iMessage recipients.
For the telcos, why would they upgrade their size limits for MMS - it's just a cost centre for them. They probably make more by selling more iPhones as well.
It's entirely up to Apple whether to make their iMessage platform available on other platforms.
They've shown they're quite invested in keeping it to running on Apple hardware only by going after and blocking any 3rd party attempt to provide iMessage compatible clients.