Apple would rather Android users feel isolated and thus pressured into adoption of a superior product than enhance iMessage to be RCS compatible. In Europe, people rarely use iMessage for group chats at all, WhatsApp / Telegram / Threema / Signal are defacto group chat apps for this very reason. People know iMessage is not multi-device friendly and no benefit to using it. I imagine this problem is nowhere near their list of actual problems worth looking at.