I think the issue with the tablet is the price (yes all apple products are expensive) and that the tablet is a secondary device. Unlike the phone which is used every day and is needed for day to day tasks, people can get by without upgrading their older iPads. I see little reason to upgrade my Mini and my wife is on a first gen Mini and she's happy about it.
They always have, I remember owning a Powerbook back in the day and the same day I bought the computer, I had to go out and buy ram for it (not apple ram, that was ridiculously expensive). At least Apple has been consistent though out the years