First off, the Adonit styluses "look" and "feel" good but don't work well for very long. They have a huge flaw in the design of their tips. You will start to see skipping lines and poor responsiveness starting somewhere between 1 day / 1 month of use.
Best stylus I've four so far is the Go Smart Stylus. Not too dissimilar from the Adonit Jot line up, but a far more workable design. They simply work and they work very well.
I strongly feel that Apple should make a stylus for their own products. Clearly, the product they've made has turned out to be a platform ripe with uses that would be optimized with a proper stylus. 3rd party products have come a long way but something official would make a world of difference. The area of the screen required to register a touch could be reduced in size allowing more precise input devices to be used with their products.
Comparing a stylus to a printer is ridiculous. They don't make cars or coffee makers either. They do however make tablet computing devices which have a slew of art, writing an notes applications, all of which would benefit greatly from an optional, precision input device.
Samsung has done this. And in that their tablet has a stylus is probably the biggest reason and selling point I've heard in why to choose theirs over the iPad. Apple could squash that easily.