They know very well that they have a ton of artists using iPads in their userbase, and a lot of drawing apps, too. I don't think they have a good reason for not making active digitizer pens for their iPad other than the fact that they don't want to seem like hypocrites after Steve Jobs' comment. But hey - it's already too late for that. They've already made a 7" tablet, too - so they are hypocrites - and might as well do this, too.
I think we'll see Samsung expand on the pen idea in the coming year (rumors point to Galaxy S4 having a stylus, too), and I intend to buy a next-gen Galaxy Note 10.1 tablet next year, as well as recommend one for a fashion designer friend. I wish they were Google-blessed Nexus devices, so I don't have to deal with the Samsung-only custom apps for the S-pen, but it doesn't look like Google cares too much about active digitizer pens right now, and Samsung's Note devices and their S-pen are currently the best on the market for this.