Plus given there was probably nothing left of it after the sets were struck when the first series was cancelled, they wouldn't have been keen to rebuild it or pay the actor/extras to fill it.
Right. They rebuilt some of the sets, but the bridge was a huge, elaborate set that was far too expensive to reconstruct or reuse, so they replaced it with a tinier, cheaper bridge set -- which was only occasionally used, since now all the decisions were being made by Doctor Zee in his temple of TVs.
Just did an image search for the 1980 bridge. What a crap set. Would have been better not to have even built it.