Neither is the HTTP specification. Nothing is stopping you from running a Gopher server on TCP port 80, should you get into trouble if it happens to crash a particular crawler?
Making a HTTP request on a random server is like uttering a sentence to a random person in a city: some can be helpful, some may tell you to piss off and some might shank you. If you don't like the latter, then maybe don't go around screaming nonsense loudly to strangers in an unmarked area.
Neither is the HTTP specification. Nothing is stopping you from running a Gopher server on TCP port 80, should you get into trouble if it happens to crash a particular crawler?
Making a HTTP request on a random server is like uttering a sentence to a random person in a city: some can be helpful, some may tell you to piss off and some might shank you. If you don't like the latter, then maybe don't go around screaming nonsense loudly to strangers in an unmarked area.