This is a weird way to think about it. You are basically saying a company should not launch something exclusive to their platform or ecosystem, but rather should consider launch a generic product compatible with everything out there. Why would they ? How will they stand different if everyone does that ?
Exclusivity is a basic part of business model. Look at PS4 with exclusive titles. Hell, look at your local store with exclusive products only available in their stores.
I would have agreed with you if Apple had done this for a basic feature like calling. But this sure is a privileged feature and there is nothing wrong in making it exclusive to iPhone (but they haven't you see).
If you feel your ability to interact with your friends and family is threatened by some business launching a service, you should seriously question your friends and family and/or your and/or their social/communication skills.
The self-entitlement is getting old. Nobody's forcing you to switch platforms. If your Apple-friends send you an invite, you will not be shunned from the event. Yes even the uncool non-Apple users will be allowed to participate in said invite.
