Within walking distance of me, there are 3 libraries that have a place that serves coffee.

(Carnegie Library Oakland, Carnegie Mellon Hunt, and Pitt Hillman, if you must know.)

In addition, all of them are surrounded by coffee places, so you can stretch your legs, get a coffee, maybe work at the coffee shop for a change of pace, then return to the library for better concentration. I have studied for exams and worked on long projects this way.

A former office mate and I would often run through all the options we had for coffee. The coffee maker in our office and the beans my office mate ordered from Hawaii. The sludge in the lounge coffee maker. Walk down the hall to the department's espresso vending machine (which makes surprisingly good latte's). The stand selling coffee and espresso one building over. Or walk about a block to the two coffee shops across the street from each other (Starbuck's and a local place).

Is coffee culture taken to such extreme in other places, or is this a Pittsburgh thing?

Some libraries have coffee shops, some allow coffee in covered mugs. This varies from city to city (and occasionally branch to branch), of course.

The main library I occasionally work at does have coffee, and is allowed anywhere on the 1st floor. You just can't take it up into the stacks.