If you want a cup of approximately coffee-shaped liquid in the morning, Starbucks is great because it's the same coffee anywhere. It's not inspiring, but it's nearly always edible. For a very large number of people who drink coffee, this is the goal and starbucks delivers, anywhere, anytime.

If you want a coffee shop experience, with young bohemian college students or starving artists or something, starbucks tends not to deliver. Being standardized lends an air of inauthenticity, and depending on what you're looking for it's a bit too busy what with everyone ordering coffee all the time so they can get through the day. There's usually some people on a laptop, and there are a few that have managed to become havens to the right type of people, but it's less "coffee shop" and more "a shop that sells coffee."

So basically, starbucks is servicing a niche market. Fortunately for them, it's a large niche, and they've self-selected for high-functioning addicts so the business model is sustainable.