Please don't get your realism in my FreeSpace. They're there because they look cool.
If FS were realistic, fighters would rarely ever be fighting within visual range since targeting would be so advanced, you wouldn't hear anything except the sounds that originate from or make contact with your fighter, explosions wouldn't be so drawn out since there's no oxygen to make a fireball, the so-called "photon" beam cannons wouldn't be nearly as visible as they are (example: laser pointer), capital ships (with their immense engines) would in fact likely be faster than most fighters, weapon damage would be ridiculously different (or weapons would shred enemy ships in no time flat - FS weapon outputs are crazy), and Alpha 1 would be able to talk.
Also, Klaustrophobia already made the same point about nebulae.
FreeSpace is far from realistic. Rule of Cool ftw.