Although in the States, most people don't use WhatsApp by default unless they regularly text overseas (which most don't). I have it installed but there is like one person who I very seldom use it with. Another person I use Facebook Messenger with. Work folks I often use Google Chat for. Everything else is SMS/iMessage and, as a non-teen, I absolutely don't care what color the bubble is (unless there's some cost implication for international texting).

Text messaging is free for the most part in the US--and most people don't care about encryption details--so it's natural to just use what's built in.