Possibly because some bridges don't have the door for it. for example, the Nomad bridge and it's variants have only two doors, one used for the ready room, and the other needed for the turbolift. While they could make it that you would just use the turbolift to reach it, some people would probably disagree with that. It might come down the pipe later on, to allow time to integrate them into all bridge designs.
Is this observation lounge different from the lounge found on the crew deck?
No, it isn't. This 'true' observation lounge is clearly derived from the ones in TNG and the TNG films. It is not a part of the current S2 ship design. It is an instance and your character has to beam out to leave it.
You can get the mission when you next travel to DS9. It appears as soon as you approach the station.
I believe a dev posted in the Tribble forums that they weren't "attached" to your ship interiors yet, because the new mission tech they need to have missions occur in our ships isn't ready yet, or something along those lines.
In short, its a tech problem that will get fixed, eventually.
Comments
No, it isn't. This 'true' observation lounge is clearly derived from the ones in TNG and the TNG films. It is not a part of the current S2 ship design. It is an instance and your character has to beam out to leave it.
You can get the mission when you next travel to DS9. It appears as soon as you approach the station.
In short, its a tech problem that will get fixed, eventually.