With so many Android phones, different phones need different drivers for the radios, video, etc. The problem is the manufacturers don't update their drivers in a timely manner. It is then made worse by the mobile carriers, who like to add their own bloatware to the phones and, even after the manufacturers release a new version for the phone, don't release their "version" of the updated OS to phones on their network.

Now, most people who want the new Android versions can get it by rooting (jailbreaking) their Android phones; just that most people don't want to do it and that it typically is considered to void the warranty.

I'll agree Google needs to do a better job of making updates available for older phones. They should be able to work with manufacturers to get the driver upgrades in a timely manner and then push the upgrades themselves (similar to what Apple does).