As soon as a new OS is available the previous one is considered old, out dated. Not necessarily obsolete but not as current as the newest OS. Guess I'm used to IOS and updates coming to all devices at the same time. You'd think all the companies producing the devices that run android would be on top of their game with the updates. Can't expect but so much I guess.
First off, the phone manufacturers can't do anything until Google finalizes the base code. Then the manufacturers all have to add the custom addons for the phones the update's going to be available for (especially things like the Note series with the S-pen), or some phone's specific features wouldn't work. Then they have to make sure those updates actually load and install properly and are (relatively) bug free, if not, they go back and get modified and tested more. Once that's finally done, then those updates are sent to the carriers who have to molest the code in their own special way, test *those* changes, and fix things they've broken.
Plus, if the phone manufacturers jumped on Lollipop 5.0, instead of 5.0.1, we'd have all the bugs that 5.0.1 fixed, as they'd have to go through all the update process as above for 5.0.1 after 5.0. Waiting to see what happened with 5.0 before jumping right on the Lollipop bandwagon, while in some ways annoying, saves the end user from having a buggy update they need to wait months to get fixes for.
I want lollipop too, but I'd rather wait and have a better end user experience, then get it rushed and have lots of annoying bugs that were fixed.
And, while Apple is able to get their updates out to 'all' their phones at the same time, how about that one update they had to emergency pull because it made phones unable to make calls? Yeah, they're not perfect either and sometimes getting the update the instant it's available doesn't work out the way end-users hope it would.