Your SIM card is your identity
I remember the time many years ago when I would get a new phone along with a new SIM card. One of the most important things I did right after registering the SIM was to change the default PIN code of the SIM to something more secure.
It was simple logic: if your phone would get lost or even worse stolen, someone could use your SIM card to make international calls on your behalf and you would get charged an immense amount of money.
Also, most phones many years back wouldn't even work without a SIM card inside. Your SIM card was truly the key to your phone.
From 'the key to your phone' to 'just give me data'
As years passed by and technology advanced, SIM cards became less important to run your phone. That was also the time when I completely removed the PIN code from my SIM card. I wouldn't care if someone had my SIM card as I already had unlimited calls/texting/data, the important part is the phone itself and it could be used with any SIM card as long as it comes with data.
And this is the primariy purpose of SIM cards nowadays, to enable data on your phone to access services like social media, messaging, the web. It became a means to an end.
In my case, I hardly use my actual phone number anymore. The most important services on my phone are texting and calling (via Telegram and Messenger), using social media and of course browsing the web.
Your phone number is now your backup plan
Due to security measures however I happen to use two-factor authentication (2FA) on most of my online services, including email. The truth is that the person who has access to my email inbox has access to (almost) my entire digital life. So of course, 2FA makes sense and decreases the risk of unrestricted access.
But there is more to that, services like WhatsApp are closely connected to your phone number. In fact, you can't use WhatsApp without a phone number and the same is true for other messaging services messaging services.
It's interesting to see that your phone number and hence the (primarily) physical SIM card became much more important than it actually has ever been. Whoever has access to your SIM card now has access to a variety of services connected to your online identity.
What if you don't have your phone number anymore?
Last Thursday I went to my local telecom provider to get a backup SIM card just in case my phone would get lost or stolen – and it turns out, I can't simply do that.
I was told my card has actually to get lost before I can order a new one, in the meantime I would hence lose access to most essential online services.
What if I'm not in the country for some time or on a trip? Good luck then.
Telecom providers need to rethink the importance of their clients' SIM cards and should allow to give out backup cards at no extra cost. Your phone numbers and therefore your SIM card increasingly becomes your online identity.