> The internet has fossilized at 1500 byte MTU.

the internet has a whole bunch of non ethernet stuff, a lot of which has different frame sizes. Its totally possible that backhaul is running jumbo frames, or something like it, but you'd never really know that.

Conversely ADSL has odd frame sizes(inherited from ATM; 48 bytes if I remember correctly), but you don't see that because its hidden from you. Cable has a frame sizes ranging from ~500 up to 2000 bytes. Again, hidden from you.

One of the joys of TCP/IP is that different frame sizes are handled for you. Sure it might be beneficial to have a frame size that marries up with packet size, it might not. you don't really know, because the internets.