tarangwydion: I read somewhere in this forum before that the problems are likely about getting the licenses with Paramount Pictures or something...
Indeed, while naturally we don't know for sure, that the license is owned by Paramount while the games are owned by publishers (i.e. multiple rights holders for each title) does seem to be the most reasonable reason why Star Trek games are not here. Pity, I too would like to see them here.
@OP you can go to the wishlist and add/vote for Star Trek games. GOG unfortunately is not in sole control of their appearance here, but it *might* help them decide to focus on getting those games from Paramount/the various publishers and to convince those rights holders to sell here. You never know.