It’s really simple, really. When WhatsApp first came around sending SMS in many places like in Europe was not free. It wasn’t free to send SMS to other people

It’s really simple, really. When WhatsApp first came around sending SMS in many places like in Europe was not free. It wasn’t free to send SMS to other people from the same country, and Europeans, especially European Students going to university will typically have friends or contacts with different country codes because they didn’t get a new SIM card for various reasons. It wasn’t free to SMS people in the same country, and it was not free to SMS people from other countries. WhatsApp changed that, without needing you to sign up for an account somewhere and telling people “my AIM is this” or “my email is that.” You were already giving people your phone number when you met them, and WhatsApp was compatible with that. So it requires no extra steps. Just download the app and go and now you can SMS people for free using the contact information you already have, using the contact information you were most likely to give to people you just met. That was the appeal.