> which is aburdly wasteful of the possible ~65k inbound ports
What is being wasted? It's not as if those extra ports have additional bandwidth or processing power available to them that you wouldn't otherwise have. You also need a spare port if you're going to do any outbound connections.
Worst case, as far as I can see, is that CGNAT providers might require more outbound IP addresses than they might ideally need if more ports were actually used; but in the general case, there is no reason to care about "wasted" ports.
what is wasted?
IPs.
not like IP addresses themself were not an actifical limit - but let set aside this for now.
if i setup an MX, it still needs to be on port 25, because the vast majority of MTAs are not capable of service discovery; and there is no Host header or SNI/ECH for SMTP, so for each mail.DOMAIN.TLD i have to buy an IP, just to put them over a single multi-domain postfix/exim in order to please those MTAs who are requisiting the HELO name to match to the MX's reverse record.
how wonderful a world-wide adoption of rfc 6186 would be to able to put multi-domain mail server on a single IP.
What is being wasted? It's not as if those extra ports have additional bandwidth or processing power available to them that you wouldn't otherwise have. You also need a spare port if you're going to do any outbound connections.
Worst case, as far as I can see, is that CGNAT providers might require more outbound IP addresses than they might ideally need if more ports were actually used; but in the general case, there is no reason to care about "wasted" ports.