Scalable Instances

Why oh why can't Blizzard make instances scalable to the number of people who enter?(It should be noted that my main is covered in "welfare epics" and my other 70 has simple blues and greens because this is all the content I have time for, not because of leet puprz)

It burns me up to think of all the content in this game that I will NEVER see. There is absolutely no way most people will ever get to see the best parts of the game. I don't care about the gear. I just want to see the zones and experience the fights.

I don't understand why Blizzard does it. Why do they develop so much content only to restrict it to the few people who have the time to spend 4-5 hours a day playing? Don't we all pay the same amount? Why can't instances be scalable? I don't expect to have the time and flexibility to be able to be the first person to see the new content but sure as hell want to see it eventually!

It happened first with BWL and Nax when TBC came out. These places are all but deserted now. Now it is destined to happen again with most of the BT, Eye and who knows what else once WotLK is released. I guess I can always keep raising my rogue in hopes of stealthing parts of it at level 80.