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.
Android implemented RCS and Apple dragged their feet in implementing the standardised platform such that high quality messaging was seamless and agnostic between brands
The iPhone needed to reduce the quality of pics/videos to non-iMessage recipients because Apple didn't support any other form of non-iMessage messaging.
Thankfully we have Signal, which solves the problem better than either platform option.
I have almost no way to convince anyone other than people very close to me to use it due to the (lack) of network effect. If they could just use it instead of the default messenger then it's a dramatically easier sell.
Obviously it's up to the Signal Foundation about the direction they take but I don't know if I've seen anyone agree with the justifications.
Google and Apple wrap up their locked down BS with SMS for the same reason. It's by default free of network effect but passively pulls people in.
Or more specifically: it's a different product ("Google Messages") that just happens to be based on RCS.
They do have some partnerships with hardware manufacturers that ship Play on their devices, and they will preload Google Messages in there as well.
In essence, it doesn't exist in AOSP, and doesn't really live side-by-side with a normal messaging app (i.e. one that only does baseband native messaging), I wouldn't be surprised if the partnerships and preloading conditions state the manufacturer can't ship their own version (I think at least Samsung had to drop their own "Samsung Messages" app as reported in one of the reviews of a foldable display phone).
In a way, RCS made no difference, and whatever Google did was mostly just to compete with Meta (both FB Messenger and WhatsApp). Fun fact: Google Messages is closer to Matrix than it is to iMessage in terms of comparable technical features.