Why does Guinness have a special pouring process / bottle, while other stouts do not? Guinness is sold in bottles and cans with special nitrogen widgets; the taps are specially rigged to have a two-step pouring process; heck, there's even a certificate given to people who learn how to "pour the perfect pint" at the Guinness factory in Dublin.  My question is: what makes Guinness so special? Why aren't these tactics used by other stout (or similar variants) producers?
Guinness is "carbonated" with nitrogen, where most beers use carbon dioxide. This requires different hardware, bottling equipment, etc.

If you've ever witnessed the appearance of a perfectly poured Guinness, and paid more than $5 USD for it, you'll understand why. It's partly about presentation. As one of the oldest beers on the market, it requires us to jump through some hoops to ensure we are enjoying it correctly. In short: I think it's mostly marketing!