[humptybumpty]

I’ve used Whatsapp since 2012.

Driving force with 20-30 somethings in early Whatsapp days in Europe was simply the first viable group messaging and sharing photos.

And the simplicity of onboarding! It immediately checked all your contacts to see who uses whatsapp. All other apps used usernames and invites. This worked immediately.

It worked on both phones, so everyone could join the group.

Free SMS was ok, but operators offered typical packages 500,1000 or 3000 free /month so it wasn’t an issue for anyone with a job. But for some it was great.

Combine these three factors and it spread like wildfire in few years.

[Leherenn]

Free international messages/calls as well. That's how most of my friends and I started using it: studying abroad is pretty common in Europe with Erasmus, or even simply vacationing.

Before that, we were using Skype, but I remember WhatsApp being so much more convenient/better, especially on mobile.

If it would have been very costly to send an SMS/call a different US state, I bet WhatsApp would have taken in the US.