[thirdsun]

You have to know WhatsApp's user base to understand this. Here in germany it's the de-facto standard communication platform. Everyone and their mother uses WhatsApp - and I mean that literally: Lots of old, non-tech-savvy folks use the service - the kind that even see creating an account as a barrier big enough to not use the service. I still think using the phone number as account was a genius move that enabled wide-spread adoption. Anyway, my mother and her peers don't have a Paypal account, no credit card (this is germany after all, credit cards can't be expected), certainly don't have a payment method attached to their Apple ID or Google Account (You'd be surprised how many people only use free apps). Yet all of them use Whatsapp happily and quite frictionlessly.

These folks are very wary of subscriptions, regarding them as potential scams or traps and while I'm sure Whatsapp would be successful even with a recurring price tag, I'm confident the service would be nowhere near as ubiquitous as it currently is.

[chosenbreed]

Okay. But not so long ago people had to pay for WhatsApp, no? Has the user base grown tremendously since it became free (i.e. because it became free)? One of the points made earlier is that before being bought by Facebook WhatsApp was a profitable operation. If that was the case then there is clearly an argument for having a relatively low cost subscription based offering...

[thirdsun]

I'm not sure if they actually ever enforced their payment/subscription. I certainly haven't been charged, but I was a user before that started if I remember correctly.

[krageon]

It didn't "become" free. It has always been free for some significant fraction of the userbase. As was mentioned repeatedly all over the comments here, many people have never seen the payment screen at all.