I have my reasons...
The psychological barrier.
For a long period of time, shiny ships and mods were totally out of my reach. The ISK was tight. Skill points were tight. Eve knowledge was tight. Yes, shiny stuff (faction, DED, pirate or officer) can bring a plus to your flying experience from early ages since they have the same requirements as a T1 module (with slightly better bonuses and stats; many better than T2 modules). But they come with a price. A price I wasn't able to pay. Things changed now. The ISK, skill points and eve knowledge aren't shiny stuff blockers anymore. But the psychological barrier still exists. Even for that dirt cheap Shadow Serpentis Kinetic Plating (selling at 49k in Dodixie). Plus the fact that I don't like showing them on the loosing part of the kill mail. If I ever get shiny stuff... It's for my private collection!
The bait.
Yes. 90% of shiny ships are baits. Or they have heavy reinforcements. Thus I, as a solo/small gang casual PVP-er, will avoid. Because I don't want to get blobbed. I would rather engage 2 Drakes in Old Man Star than a single Harbinger Navy Issue. Or a T3. I wan't people to be interested in my ship. I want them to try to engage me and get a fair fight instead of either repelling the exact typology of pilot I am looking to fight, either attract the exact typology of the pilots I am looking to avoid.
The Pinata Factor.
If I find a faction spawn in a belt, the faction ship will be my primary. If I pass an ongoing fight, the shiny ship will be my primary. For the same reason. The drop (+ the shiny kill mail). So, why not use this in your favor? I want the occasional soldier of fortune fighting by my side, not against me. Yes, that can also escalate on the other side. But most of the times they will go for the shiny ship.
So, yes. I don't fly shiny.
90% of the time. Because it feels damn good flying shiny and winning. You feel like you cheated death. Again. And again. Next time you see a 'fs' ending a conversation, think about it. Maybe it's not a shorthand for "Fly Safe"
FS 'till next time!