Earlier quoted context omitted.
WhatsApp, nothing more than another internet messaging app that requires data, shot to popularity because it fooled users into thinking it was somehow an SMS client because it used phone number as account.
No, because it was (and probably still is) the only messaging app that works with feature phones.
Sadly, Facebook has since dropped feature phone support to support their flanking maneuver on Snapchat (Instagram on the other flank). Instead of keeping WhatsApp simple and admitting it was feature-complete, the grand plan seems to be "copy features from Snap, and drop feature phones that can't keep up".