SMS (short message service), or text messaging, is a winning product. It’s the best possible solution when I non-urgently want to get a hold of a family member or friend. As such, it’s the first solution that comes to mind.
Text messages follow the two rules: it starts with a single primitive (the text message) and uses existing solutions (text, images, etc.).
A text message uses familiar solutions. Text, of course, but also links, gifs, and images. Nothing in a text message feels unfamiliar. On modern devices, you can also send audio messages and more.
Typically text messages are tied to your phone number. Another familiar solution. You could text with an app like WhatsApp, but then you’d have to download and learn to use a new app. WhatsApp is not a winning product for grandma, but it might be a winning product for someone else.
If I had family and friends who lived overseas and had to pay international SMS rates, WhatsApp might be best-in-class for me. WhatsApp might be the winning product for people messaging country to country.
If I was extra careful about privacy and security, I might use an encrypted messaging service like Signal or Telegram. Privacy might be so important for some folks, that one of these apps comes to mind before a simple text message does. For privacy-minded individuals, Signal might be their winning product.
For most of us, SMS makes the most sense because it uses widespread solutions like phone numbers, text, and images. This makes it easy to communicate with people owning a phone, and with content that we’d both understand. If we want more specific features, like richer content (Snapchat, TikTok, Instagram), or international communication (WhatsApp, Messenger), we could choose those products instead.
SMS has been a winning product for a while.