a bit disappointed this only points to ethernet as its answer. it does help to understand why ethernet requires addressing versus some others that do not.
Notably, none of this implies IP. IP was the expensive DARPA project that the military was building out. Ethernet is just "I am machine X, I want to talk to machine Y, here's some data". It just so happens that Ethernet was very popular, and people wanted to route IP over Ethernet. But you could route all sorts of other protocols over Ethernet as well and it would more or less work. So now we need two different classes of addressing: one for just the local network, and one for the IP network running on top of it.
And to make matters even worse, we don't use Ethernet in its original configuration anymore. First we replaced the loop of coax and vampire taps with 8P8C wire and passive hubs, then switches got cheap enough that we stopped making hubs. Ethernet framing also wound up being used for Wi-Fi, except like 99% of all Wi-Fi connections are in Infrastructure mode running IP anyway.
If Ethernet had been built to run IP exclusively, we wouldn't need Ethernet's header or MAC addresses at all. It would just need to encode IP packets and their boundaries. Even IPv6 wouldn't need a separate header as IP has its own version field.
[0] MAC addresses are supposed to be unique, but let's just say it's "LAN-scoped" and leave it at that.