The writers' intentions don't constitute canon though -- unless what they intend is actually established on-screen. And you don't even know that was what was in their minds: even in the U.S., even in the 1980s, women keeping their original surname wasn't unheard-of.Uhm, I can concede that only because nothing on screen contradicts it, but let's be serious, an 80s tv show: of course in the mind of the writers she got husband's surname.
So? Does it only count if their intentions were pure?Well, this is possibly just for marketing reasons. So you don't have to re-label all the merchandise.
I always had the impression that Betazoid culture was matriarchal (not sure why; was that ever actually established or is that just my personal headcanon?), in which case it would certainly make sense for the husband to take his wife's name. Or perhaps Ian would have (and Riker could have) taken his Betazoid spouse's name in recognition of the Troi family being part of Betazoid aristocracy,I always thought that was what was implied by Picard calling Riker "Mr. Troi" -- that Betazoid custom was for the husband to take the wife's surname.