Seven years life isn't bad for a laptop, and it cost about the same as a high end TV set at the time. Why is it reasonable to have free updates on one, but none at all on the other?
Because margin, that's why. Apple makes a fat profit on every device it sells, so it can easily amortize the R&D costs of keeping the OS up to date. It can even afford to give major releases away for free as an incentive to get on board with the platform (although major updates weren't free in 2008 when your laptop was made).
TVs are a whole different market. The margins are wafer-thin or in some cases non existent, as you can see from the red ink in various manufacturers' financial results.
I'm not trying to excuse this short-termism, just pointing out the reasons for it..