I think you are underestimating the degree to which requires only a phone number is a killer feature:
-you download the app and can immediately get started after verifying your phone number (no ID or password required)
-you don't need to share any ID or connection details other than just your phone number
I spend a lot of time in India, and I think this lack of complexity has contributed significantly to its virality (I'd estimate that a pretty significant percentage of the user base does not have or regularly use an email account, which is usually a prerequisite to setting up many accounts).
Whatsapp has replaced SMS as the defacto standard mobile messenger for 98% of users in Europe (or many other places). It doesn't matter if they do things badly, there is no way around them at the moment.
It is even replacing SMS more in areas where Facebook pushed their internet.org / free basics program, where mobile network companies where supported by Facebook to grant free access to Facebook services while still charging for SMS (or other websites and services) There WhatsApp is/was free. (A few years since I looked into it last, not sure how the project changed)
An anecdote from South Africa: SMS was charged per message at very high rates. MMS even higher. Mobile data, while expensive too, was much cheaper per message. Also, free wifi was quite common in many urban areas. All this at a time when WhatsApp was much much simpler and easier to use, with good UX. The person to person advertising for WhatsApp at the time was “it’s free”, which while not 100% true factoring in mobile bandwidth, it was effectively true since mobile data and WiFi was at least 1 or 2 orders of magnitude cheaper than SMS or MMS.
That stayed true for a few years, and so WhatsApp became the de facto standard for messaging.
I can’t speak for other countries but in South Africa that’s why. And the rest is just networking effects.
Ah, that makes sense. I'm fortunate enough to live where we have unmetered SMS/calls/data so I've never had that issue (at least not while WhatApp's been around).
My phone number is an ID. An ID I don't want to share. An ID that can be stolen by calling the phone company and saying you're me and bought a new SIM.
Then you need to realize that you are a special case and not representative of the general public.
Most people who meet each other in real life and want to exchange contact information exchange… you guessed it… a phone number. Maybe you exchange email or twitter handle, but again you are an exception here. So imagine we meet for the first time and we exchange phone numbers. Now I can WhatsApp you, just like that no other account info needed.
You can get replacement SIMs with the same number (source: I'm in Germany and on my third SIM with my current number after first not having a micro-SIM and then a nano-SIM) – I did get notofied of this by SMS, though, and no idea what other anti abuse measures may be in place. I can order one for 10 Euro via the website anytime and I suppose I could do it via phone as well.
There was actually a scandal about that in Denmark recently. Some journalists managed to get new SIM cards for other people without proper authentication. Repeatedly and from different providers.
As I've heard it, the alternative that drove the first hundred million users was the telco reading over your shoulder and/or randomly dropping your messages on the floor.
Whatsapp grew big with customers of telcos like Vodafone, which may be less capable than Mark Zuckerberg's snoopshop but I wouldn't bet on their being nicer. See https://toroid.org/vodafone-smtp-mitm for example.
-you download the app and can immediately get started after verifying your phone number (no ID or password required) -you don't need to share any ID or connection details other than just your phone number
I spend a lot of time in India, and I think this lack of complexity has contributed significantly to its virality (I'd estimate that a pretty significant percentage of the user base does not have or regularly use an email account, which is usually a prerequisite to setting up many accounts).