Why fighters? Real simple. The stations shielding is good, but not
great; fighters could punch a hole in it. So on that level, they're there
for defense. But aside from that, B5 is charged with being a port of call,
and thus must keep those traffic lanes in its general vicinity safe. So
fighters are sometimes called upon to protect civilian vessels from a
variety of threats. Also, if a ship is disabled and unable to find the
station, or otherwise hobbled, a fighter escort can be sent to get them
to the station. They're *very* useful.

jms

(P.S. Just a thought...but I've been watching the discussion of the
Starfury launch sequence with great interest, particularly in light of the
fact that only -- what? -- 20 seconds of B5 material has been released,
and that alone has triggered off a detailed scientific discussion of
rotational gravity, centripidal force, and other aspects of physics. I
can only wonder what more detailed discussions will be triggered once we
actually begin showing whole *episodes*.)