Think of SOAP (and webservices) as a method for doing RPC over exisiting protocols such as HTTP using platform independent data (i.e. embed everything as XML)

This changes the question to be "why would I want RPC?" -- Which is all down to the problems you're trying to solve. To pick a problem at 'random'; Let's say you want to find events near a UK postcode -- you may not want to try and collect this data locally, and might want to pull data off an existing website like local.angle - they offer a webservice that allows you to get a list of events based on your postcode with their permission -- you could just pull the data off their website, but you do have some morals, right?

For the data providers (in the case of web services that merely retrieve data) it's a lot more efficient to give the raw data, instead of the data dispersed through the virtually manditory 30kb of navigational fluff that is merely presentational.

Now, expand this to the cases where you want them to do something with your request (like order some books) and it becomes even more of a saving, as you're not having to "fake" form filling, etc.

Other examples I've seen (and used) are the ability to query the Amazon catalogue, find out about DSL and cable modem availability in the UK and getting exchange rate data.

At then end of the day, it's up to you to decide whether web services will solve your problems, and whether you'd like to reuse the services out there.

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RatArsed