Jokes aside, I see SMS as a useless protocol; because it cannot be used for identification, and neither can anything be encrypted nor verified without another communication channel.
It's also not in the power of the end user to decide whether or not their number gets reassigned, blocked, or does work at all. Most US people seem to think that it's normal to have "one" number for years on end. For the rest of the world, it's not true.
For example: If I don't use my SIM card to make phone calls (which get billed) for 6 months, it's gone and reallocated to a different person.
Uh, I’m from Germany and had the same mobile number for over 20 years.
It's a ̶̶u̶s̶e̶ pay it or lose it thing. AFAIK, typically applies to prepaid/pay-as-you-go SIMs, not on contracts.
For my case, it is that I have to make a 12EUR top-up every 3 months. The top-up credit will expire if I don't make another top-up on time. After a few months on zero credit, you get you incoming calls blocked. And after a couple more months, your SIM is de-registered.
Transferring your number is always possible, yes. As long as you're still the registered owner of the SIM number.
Even two years ago, I had to actually change a phone number because I couldn't transfer my number from one provider to their own reseller. O2 Scheißladen.
Huh, I guess I got lucky staying with Viag Interkom and then O2 (which was an automatic switch when O2 bought them) for so long, I only really switched providers in 2020 which was long after the EU regulation was in effect.