I meant “in the same way that phone numbers are unique to phones (not perfectly unique, some phones have dual Sim, some have no sim, sometimes a Sim changes numbers after contacting the provider, etc)”

Its just typing all that^ in a title is kinda long.

EUI-64 IPv6 (and why its not a reality) though is kinda what I’m curious about. But not really because, even under that spec, its still a MAC address. Its not static like a phone number. I want to know why networks were not created in a way where I can send a message to a laptop regardless of what WiFi its connected to (assuming it is connected and online).