Many reporters go on and on about about the fact that Android Users "don't upgrade".
Some of the more intelligent realize that is the phone makers that don't upgrade.
But both sets are fundamentally wrong.
The reasons there are so many Android 2.3 users is that phones are still sold using 2.3. The simple fact is that 2.3 is reasonably functional and that the cheapest phones are only able to support 2.3. This is a good thing as people that could not otherwise afford the phone can get one. Outside the US where phone subsidies by contract are usually not done, this is particularly important. This will be changing soon as faster hardware is getting cheaper, but a new pool is forming around Android 4.0 (ICS). There is definitely hardware out there that should not move beyond 4.0.
While some phone and tablet makers are slow about getting upgrades out, by and large most phones and tablets that can be upgraded eventually get the upgrade.
Here are some samples:
Android 4.x finally surpasses Gingerbread in OS share - AfterDawn
Android 4.0 (ICS) + outpaces Gingerbread share | TG Daily
Android version distribution: February 2013, Jelly Bean gains slightly | BGR
Ice Cream Sandwich and Jelly Bean Are More Popular Than Gingerbread | Gadget Lab | Wired.com