Swifts and Swallows

I have been wondering why Swifts and Swallows are not together in my bird book. i.e. are not in the same family.
So I googled it and found this:
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The swifts are a family, Apodidae, of highly aerial birds. They are superficially similar to swallows but are actually not closely related to those passerine species at all; swifts are in the separate order Apodiformes, which they share with the hummingbirds.
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The resemblances between swifts and swallows are due to convergent evolution reflecting similar life styles based on catching insects in flight.
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Maybe someone else was wondering that as well.
Convergent Evolution was the answer that I was looking for.
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cheers,
steve