Because fluff is important. People love and play the game because of the Star Wars universe, not just the game mechanics. And the more FFG gets into obscure EU stuff the more they diminish that aspect. The Z-95 has been around since 1979 and is well-established in the setting, and was eagerly anticipated. Same with the TIE defender, a ship anyone who played the PC games that inspired X-Wing will remember. But now look at the wave 5 ships: "Han is unavailable, stick a new name on the character" and "imperial players keep whining about not having a turret ship, is there anything we can give them?". Now imagine a completely new ship with even less connection to the universe than the Decimator. Can you really imagine many people getting exited about it, outside of how it will help them win games?Plus, there's a big quality issue to worry about. So far the game has been driven by a need to represent the important ships, and FFG has done a pretty good job of it. Ships have a clear role, characters are interesting, etc. But will they be able to keep it up when they run out of relevant ships and have to start digging for obscure video game ships that nobody has ever heard of, just to keep sales from collapsing?They're already releasing ships with only 1 EU appearance. It's not really much of a leap for them to just create new ships if they run out. Why not?
1. This game is based of the old X-wing games which had plenty of stuff not in the movies.
2. This is a game we should be getting excited for things to help us win.
3. Let's be honest even if we haven't heard of it we are still gonna buy even if it's begrudgingly so.
4. Digging into obscure let's us learn about some new EU stuff.

