Because all the good imps from Canderous Rerolled Pub (*Cough* LD50 *Cough*). So imps got stuck with the short end of the stick with terrabad imps coming from other servers. Only decent imps I've seen are the guys from Honor and occasionally the Try Hards.
There are still some good imps, but the imperials problem is simply battered wife syndrome. You guys are so used to losing that a lot of your players go to a WZ and don't give a damn. While on pub side there will always be players that are bad but they still try to win the game (most of the time). Nobody can really blame the pathetic state of imperial pvp on a handful of people who rerolled. It takes effort from the community to change the overall mentality.
People are a little too quick to place blame rather than fix their own crap these days.