In my games, deckplans are used, and frequently. I'm sure that they are completely unecessary in a highly narrationalist style of play, but then again so would schematics and miniatures, and the ship stats. Saying "Starships aren't dungeons" is correct as far as it goes, but rather misses the point. Dungeons are, by their nature very limited in what kind of adventures one can have, and thus tend toward very stereotyped gaming situations. Starships are different when one gets out of the "dungeon map = dungeon crawl" mindset.
For everyday use (such as going to the bathroom), and narrative parts a schematic, or even a vague drawing is fine. But, for the adventure bits, there's a lot more that can use a deckplan than just a minis Game. generally, they are situations where movement has to be optimized and traded off against time.
Examples of which have all happened in a two year game and used deckplans are: "Search the abandoned ship", "Find the bomb before it goes off", "Kill the infestations of alien vaccume resistant crawdads before they get into everything", "clear the captured ship", "rescue the hostages" , "rescue the survivors", "rescue the survivors in the middle of a firefight", "escape from the brig and seize the ship silently without shooting", damage control in a space fight", damage control in a catistrophic accident, "pilfer the ship in the next slip while in port"; and of course, the ever famous "board them,kill them, and steal their silverware, arrrrr."
And oh, yes, we have also run miniatures games in them; and keeping the more wargamy bunch of traveller players interested can't be a bad thing in terms of extending sales. So just writing that aspect off seems a bit shortsighted, and I'm glad mongoose hasn;t done that. I know that its somtheing that seems to have ots of local variance, but there do seem to be lots of people 'round here who like minigaming and traveller and do it often -like say at the next con, Gypsycomet ?