Why do some web apps use intermediate page before redirection?

Question

After editing an article or logging in some forums or CMS, you get a intermediate page that say something like "Thanks for X, if you didn't redirect in few seconds click here".

Why they do that instead of going directly to the page?

Answer 1

There are many reasons to do this; and most of them are silly:

1. The developer could simply not know how to set up server side redirects. (Silly)
2. The web application could be set up in such a fashion that certain actions that require a redirect don't allow the taking of a redir= parameter, of something of the kind (Much the same as 1, and still silly)
3. The developer could be trying to squeeze more ad impressions out of the visitors on the intermediate page. (Extremely silly)
4. The web app could be operating under some extreme "safe mode" that doesn't allow server-side redirects (Yep, you guessed it, silly.)
5. The developer could wish to be very explicit about what exactly the user just did, so as to be sure that the user knows what just happened. (At face value, this seems sensible. But whereas users literally couldn't read a status message if their life depended on it; silly.)
6. Edit: Using it instead of 303 Found to implement PRG. (Silly, see all of the above.)

Edit: When I say most of them are silly, I don't mean to say that some of them are silly, and some are not. I mean to say that some of them are silly an some are extremely silly.