Guess it depends on your circles. For my group, everyone has an iPhone or a Mac. For the outliers, everyone has cell phones, and iMessage supports SMS.
>iMessage supports SMS.
Which isn't end to end encrypted which defeats the whole point in terms of this conversation.
I've also had terrible reliability issue with imessage in the past, messages not delivering, not showing up, errors sending, showing up on one device but not another, etc. Was a mess that caused a lot of confusion.