I guess this also varies tremendously by region. WhatsApp completely dominates non-work communication in Argentina; we don't use SMS, nor phone calls, and FB is pretty much is second place.
AFAIK, in the US people actually use SMS a lot, and I'm sure it's a bit different everywhere else.
More on topic though; you can use Messenger without an FB account and still find people by username.
I guess this also varies tremendously by region. WhatsApp completely dominates non-work communication in Argentina; we don't use SMS, nor phone calls, and FB is pretty much is second place.
AFAIK, in the US people actually use SMS a lot, and I'm sure it's a bit different everywhere else.
More on topic though; you can use Messenger without an FB account and still find people by username.