I don't mean to criticize or anything, just mean to understand. There are so many people who are very passionate about Haskell that it makes me think that it must be worth while to learn. But I just don't get how it would be useful for things that I do most with programming: writing Web/Desktop/Mobile apps in Swift, Python, and PHP.
Also, can you recommend a good book or resource that uses real world examples to teach Haskell?
Out of the things you mentioned, server-side programming is the one where Haskell fits best. Server-side programming is more amenable to unusual languages because you get to choose your own platform and there are plenty of mature web frameworks you can use (too many of them, I might say). It might be worth a try to experiment writing code in a more type-safe language. Even the simple things like algebraic-data-types are things I miss a lot when working on other languages.
Yes, and yes.
> Also, can you recommend a good book or resource that uses real world examples to teach Haskell?
The obvious thing to recommend here is Real World Haskell , which directly addresses some of the areas you raise.
Also, Write Yourself a Scheme in 48 Hours  is more in-depth and real-world than most tutorials (writing a Scheme interpreter isn't exactly a common real-world application, but its more real-world scale than most tutorials address, and it uses a lot of things that are of concern in many real-world apps.)
Haskell is a general purpose programming language.
RWH is well-written and covers some real-world tasks, but some of its examples are outdated enough that they don't even compile anymore (at least, I encountered that scenario a year ago or so) and Haskellers will frequently warn people that parts of it are out of date (see elsewhere in these comments).
Someone else suggested "Write Yourself A Scheme" as a good practical introduction, and that in itself says a lot about who Haskell appeals to -- people who are interested in programming languages. The MLs and Haskell remind me of Brian Eno's line about how the first Velvet Underground album only sold 30,000 copies, but "everyone who bought one of those 30,000 copies started a band".