Hmm.. I couldn't send "my car broke down" on Signal because it's one service was down for reasons entirely unrelated to my use.
One can use email and have an address at Google and one at work, and know these data points for a friend. One can use a phone and have multiple service providers (in some countries multiple sims for costs, in others legacy landlines.) One can use WhatsApp, Signal or Slack and then you need to synchronize on an entirely different backup service. None of them have the POTS guarantee and for the most part we (at least in my age demographic) don't even trust the POTS service with non-redundant numbers.
> Hmm.. I couldn't send "my car broke down" on Signal because it's one service was down for reasons entirely unrelated to my use.
This happened to gmail recently, too, and my realtor couldn't send me contracts during a bidding war. In the case of gmail, it was an accidental reduction of provisioning to an internal service (perhaps easy to predict if you ignore the enormous complexity of the googleverse). In the case of Signal, it was a result of a scaling suddenly and faster than they could be expected to predict (perhaps easy to predict, but not a certainty; a risk in any case for a small operation like Signal).
One can use email and have an address at Google and one at work, and know these data points for a friend. One can use a phone and have multiple service providers (in some countries multiple sims for costs, in others legacy landlines.) One can use WhatsApp, Signal or Slack and then you need to synchronize on an entirely different backup service. None of them have the POTS guarantee and for the most part we (at least in my age demographic) don't even trust the POTS service with non-redundant numbers.