[bvcvbuiy]

Where I live mobile plans include unlimited SMS.

Also I have a dumbphone and I am the only person my friend send SMS too. That makes me quite a unique person !

[mantap]

The point is that the penetration of WhatsApp is way higher than the penetration of unlimited SMS plans. So whatsapp has broader reach.

SMS only works if you live in a region where unlimited SMS plans are standard AND you don't have any friends outside of that region OR WhatsApp doesn't have market share there. Basically only US.