I suppose none of the others, which could have leveraged their existing userbase chose to follow suit because the companies that owned them did not have a way to make money from them. WhatsApp didn't either, but startups weren't expected to.
The initial WhatsApp plan was to charge between $1 and 2€, initially a one time fee paid after a few weeks, then a yearly subscription after one free year.
I kinda wish that had paned out.
It'd still be hundreds of millions of dollars in yearly revenue. Plus businesses.
The funny thing is that on Android, I never had to pay the fee as the free trial kept getting extended. Only my friends with iPhones paid for WhatsApp, IIRC on iOS it was upfront too!
