It's fun.
It's interesting.
It's a challenge.
With each successive kill, the excitement level goes up another notch.  With me, I'm mostly hunting buffs at alt.  If I am to continue the sortie and be able to rearm to push that kill number higher, I've got to shoot down the buffs without taking damage so I can rearm and up again.  To continue I must make my attacks as perfect as I can, and give my opponent as little of an opportunity as possible to get hits on me.
For the past year or so, I have been actively working on perfecting the 3fer on bombers.  3 kills in one pass.  It's difficult. 2fers are hard enough.  I'm doing this because a 3fer only exposes me once to enemy fire.
We all find our fun in many different ways.