You find yourself in the same position that Trillian did, what, 15 years ago?
Thanks for giving it a shot, at least. It's getting to the point where if I wanted to keep in touch with most of my friends all the time, I'd need to carry two or more devices (thanks for keeping iMessage closed, Apple).
Which is absolutely irrelevant. It's expected from a mobile phone to be able to send and receive SMSs. But SMSs can take several minutes to reach its destination in some areas. Long messages are split. And the experience as a whole is totally different. And of course, most people pay per message (individually or as a pack), at least globally. So, if someone wishes to send a message, it shouldn't matter what OS or app is being used by the other party. IF GP uses an Android phone as its primary phone, it may be problem if he is trying to chat with someone who uses only iMessage.