= Messaging software that force you to have a mobile phone
Chat programs that don't have a proper web-only operation and force you to have a mobile phone, e.g. <WhatsApp>{child}.
Heck, even <Signal (software)>{child}, which is supposed to be super secure and good for your privacy, forces you to disclose your freaking cell phone to all contacts! https://lifehacker.com/how-to-use-signal-without-revealing-your-private-phone-1818996580
What is my phone breaks? What if I don't want to have a <fucking> phone? What if I move countries and have to change the <fucking> number? Also evil but less because done by all: chat programs that can't send you an email https://webapps.stackexchange.com/questions/41528/how-can-i-automatically-forward-facebook-messages-to-my-email-or-phone[if you don't see the message in X minutes].
<Europe>[European Union], time to force those evil <companies> to use support open standards like <XMPP>?
The solution to "how to prevent spam" is simple: your ID is a public key that you own the private key for. If you start getting spammed, generate a new public key, and send it to all contacts, and dump the previous ID.