Who says they did? They had UTs on board.
It's pretty clear in DS9's 'Little Green Men' that Quark didn't speak a word of Federation Standard, once his translator broke.
Also, Vulcans and Romulans are probably just what humans call them. We have planets named Mars and Uranus, etc. So why not others named after mythology? They probably call themselves something else.
It's pretty clear in DS9's 'Little Green Men' that Quark didn't speak a word of Federation Standard, once his translator broke.
Also, Vulcans and Romulans are probably just what humans call them. We have planets named Mars and Uranus, etc. So why not others named after mythology? They probably call themselves something else.