Because loot has low drop rates, and people do not like to run instances for months and see their one drop taken by someone on their first raid. Why would you do progression raids and get no rewards when you can just wait for the farming runs and just /roll your way to loot?

My pre-BC guild was destroyed by loot vampires that didn't show up for progress raids.

Wow, you are a true loot whore aren't you? DkP is there so when a guild is pushing through progression content, the loot is distributed according to effort invested. Why should a "new" member get a T5 drop when he hasn't had to spend countless nights spending 40g+ in repair bills? Not to mention, the same "new" member may not be as reliable for raiding, so what good does it serve progression to have useful loot go to members who won't really USE it? My guild is currently pushing through TK (3/4) and SSC (4/6) and as we get the bosses on farm, we begin to get in our "younger" members so they can benefit as well but only after the core raiders have the upgrades they need to push on to higher content.

Bliz definitely made our lives easier with sensible loot tables and 25-man raids, but when dealing with progression, different rules are needed.

All I can say is I'm glad you're not in my guild b/c loot whores aren't tolerated one bit.

Why anyone couldn't understand the simple concept/purpose of DKP is beyond me.

And I can't remember anyone ever saying "everyone pass"