I've been doing a lot of writing lately and writing requires a significant amount of coffee. I drink espressi from time to time while writing, but I really like a sippable (made up word alert) drink so I've been making Americanos more frequently. I like espresso more, but I think that the Americano has its place. It appears to get a bum rap in the world of espresso; the Italians scoff at its weakness and it is a bit of a red-headed step child here.
Adding hot water to espresso has three things going for it:
Sipping: This is the big one for me. I love espresso when I'm rushing around in the morning and trying to get out the door on time. It is a nice quick burst of flavor that will linger throughout the morning. When I am working, I like a drink that I can sip for a longer period of time. I usually have my espresso machine ready to go so it is often more convenient for me to make an Americano than to change my grind, boil water, and then brew coffee using a pour over, French press, or vac pot. Plus there is additional cleaning that comes with having espresso and drip.
Taste: I'll often notice, or be able to identify flavors that I cannot pick out in a normale or ristretto. This is especially true of more complex single origins or blends. I also like the change in character of a bean when comparing it in its drip form to an Americano.
Fresh coffee at subpar cafes: When I want a non-milk drink that I can sip while I'm working, I usually order an Americano at places that don't offer a fresh drip coffee. It might not be great, but it is almost always better than drip that has been cooking for the past hour.