Regarding support for 3GS vs. iPad 1, it's not "strange" at all. The 3GS was available at retail as their entry-level device up until the iPhone 5 was released in September, 2012, whereas the iPad 1 hasn't seen shelf space since the iPad 2 came out in March, 2011. It's just a bit dishonest to judge Apple's support matrices on such a substantially different timeframe of retail availability, especially since their phones are much more a core product--some would even say, their gateway device--than their tablets.
Originally Posted by eblade
Also, not to niggle, but the iPad 3 was discontinued for the iPad 4 with Lightning connector. I have friends still bitter about buying a device that enjoyed only 6 months of retail life before literally being pulled off the retail shelves and forgotten to history. Now what you'll find on the shelves are the iPad 2 and iPad 4. Why 2 and 4? Because leaving the iPad 3 out there would have cannibalized sales of the iPad 4 while there's little chance of the iPad 2 doing the same. Think about it a long, hot second, and compare feature sets between the 2, 3, and 4 while doing so.
Apple also won't have to worry about its position in the tablet market for a while yet. Its institutional market is exploding still, and the only segment where Android is taking up the slack is in price differential. Other than that, well, Apple still owns the market it practically reinvented. And I don't even own an iPad.
On the general point, you're probably looking for the term "forced obsolescence" here. While I'll agree that the iPad 1 is still good for your mom and dad or someone consuming general media as opposed to gaming, the fact remains that, as you (astutely) mentioned elsewhere in this thread:
...many people will still be pleased with their iPad 1 devices well into the future. Because it works. And when their favorite apps begin to leverage the calls available in the newer versions of the iOS SDK, they'll upgrade. But for now, I imagine most people with iPad 1 devices are really not giving too much of a crap unless they absolutely must use the latest and greatest with the highest PPI and lowest latencies.
People don't BUY tablets because they'll get system updates on them. People don't CARE about system updates, they only care if the devices do what they want them to do.
Given how many Average Joes and their families don't even upgrade their desktop browsers until they replace the desktop, well... Draw your own conclusions. Chances are, they're just peachy with their first-gen iPad.