Completely agree.

> WhatsApp because it meant that international SMS was now free

Not sure the exact meaning of "international" here. In Brazil SMS was not free at all, so Whatsapp became a free SMS for all, with bonus of a nice chat UI that made easy to be in conversations (contrary to any phone's SMS UI at the time), groups, images (becoming a MMS for free too).

So, a 100x better SMS for free. No wonder it exploded.

But the use case was mostly for local messages, not international messages.