I bought a 4 pack of Guiness Stout Draft cans tonight.

[Major Nikon]

14. Bottled and canned beers are made to be poured

They have additional carbonation such that when you pour them after opening, the carbonation level is ideal. In many areas of Europe where premium beers have been brewed for hundreds, if not thousands of years, drinking out of the bottle or can is almost never done. As the beverage releases carbonation in the glass, the aromas that come with it enhance the effect of the beverage in ways you don't get if drinking out of the original vessel. In the case of many dark beers you also get a creamy head which lingers far longer than other beers which enhances the effect for me.

Personally I prefer draft beer to canned or bottled options all other things being equal, particularly when poured by someone who knows how to do it, especially in the case of stouts and porters.

So to answer your question there are reasons to drink beer out of a glass, which is not to say it's wrong to do it any other way. Enjoy it however you like to enjoy it.

Some people like Guinness and it's safe to say there's a good many of them given their sales volume all over the world. Fortunately for me Texas has a strong brewing tradition, so it's easy for me to find variety that goes well beyond the mass produced options.