Why integrate Joomla and Wordpress?

OK, I admit it it, I just don't get why you would want to integrate these two applications.

I just can't see where the benefits are.

1. I accept that some people think that Wordpress is the best thing for a blog, although I obviously think they are misguided.
2. I accept that some people think that they need Wordpress for a blog and Joomla for the rest of their website.
3. I just don't get why you should go to the time, trouble and/or expense of integrating the two together.

What is the point?

1. I have sat through presentations on "how they an be integrated"
2. I have seen demos and examples of the two being "integrated"
3. I just don't get why?

Am I missing something really obvious?

1. Is there some hidden secret that I've yet to find?
2. Is there a trick I am missing?
3. Or shall I just file this under the mouldy peanut butter sandwich I was eating when my opinion last mattered.

Please enlighten me if you can.

I really want to know what I am missing.