This may be ignorant, but why does green/blue bubble matter for US folks? Almost all cell providers have free SMS/MMS. Would people even notice it if the color was always blue?
Green/MMS messages end up having much lower quality images and videos than iMessages. Send the video to another iPhone user and they see it in HD. Send it via MMS and someone gets a blurry postage stamp video.
But from an Android phones perspective it is the iPhone users that have low quality images and compatibility. Whenever someone sends me an image or video from an iPhone it seems like their phone must be terrible.
These systems could work together if Apple wanted them to. Google / Android isn't the part that is preventing interoperability. So ultimately it really is an iPhone being bad problem. They've marketed the problem well to make it seem like it is the other way around in order to make iPhones more desirable.
because it doesn't allow nearly as large images/videos/etc to be sent. They either get dropped or reduced in size by various means. If you stick to text I've had no problems, if you don't you're on your own if your doing Android <-->iPhone . most of my friends use signal or whatsapp so it's not a big deal for me, but others have issues.