That’s not a good comparison. There are many alternatives to WhatsApp and it’s not a „critical“ infrastructure. In contrast, you sometimes can’t choose your ISP and internet is much more critical.
It can be in area's (such as in The Netherlands) where literally _everyone_ is on WhatsApp and it is the default form of personal online communication.
Not using WhatsApp means not being able to communicate with a lot of people.
Same with Portugal and Facebook messenger. I found a solution but it's less than ideal. I have less friends now.
Same in the UK. All my friends, family, coworkers. My boss. I've used WhatsApp instead of email to communicate with my landlord, recruiters. Some companies even use it for customer service as an alternative to phone or some terrible chat built into their website.
In the Netherlands it's so pervasive, it isn't only the default form a personal online communication anymore. Rather, it is quickly becoming the default form of online customer interaction as well.
Do not they have e-mail? That seems like safe default.
To most people, email is something that you use for work, or if you're over 50.
I use both. I realize that Facebook already has my social graph and the epsilon more information they get from my family chats pencils out to epsilon. I use Signal when I don't want Facebook to know and monetize that knowledge.
Same in Germany. You have no chance without Whatsapp. Every birthday party, every friend circle etc. has a Whatsapp group.
That might depend on where you live. Around here, WhatsApp definitely is "critical", in the sense that schools, sports clubs, business as well as social life seem to be built around it nowadays. :-(
Where I live, everything is based around WhatsApp. If you want to receive a package from Amazon/FedEx/DHL/UPS, etc. The shipment will only be delivered to the location you share with the courier on WhatsApp, if you're not on WhatsApp you can't even receive packages. There are so many other things like this that are happening only on WhatsApp, and if you're not on it you won't even be able to use basic services.
I can choose my ISP in the UK, but we have such brutally entrenched network effects with WhatsApp that it literally means not talking to loved ones and community groups if you quit.