No official uses other than multi-console local multiplayer (on a more limited number of games than PS1 serial link ones) outside of possibly the PSX, the fact firewire was/is patented by Apple (with a licensing cost per port), and of course the corner-cutting reputation of the company
The fact you could use ethernet for local networking is more of a consequence of removing firewire (network adapters weren't cheap at full retail price, in Europe it's still cheaper and better to import an American one with 56k modem since they have no known clones)