Why is resizing the browser window bad practice?

I asked how I can resize the browser window with JavaScript. Everybody told me not to do it. Why is this a bad practice?

I think sometimes it can be good. For example, I want to show users a tweeting popup page. After a user tweeted, I want to redirect him to twitter main page to let him verify his tweet. But tweeting page is small and main page should be big. In this case, making the browser window bigger seems good for user. Am I wrong? Then how should I do in this case?

Update

I think I need to make somethings clear.

  1. I also don't want my browser to be resized. Resizing users' browser is usually bad. What I want to know is that there could be some case it can be good.
  2. I also don't like popups. But as @zzzBov said, pop-outs are different. That is used in many websites even in Stack Exchange(You can see share buttons under the favorite button). I don't think it would be better if those buttons were jQuery modal dialog.

And, JavaScript resizeTo function can resize the browser. When I tested that function, it works well in browsers but Chrome. In Chrome, it works just in popups. I might be wrong, but I guess Chrome team also may thought that the resizeTo function would be needed in popups.

Update2

Most people just don't want the method resizeTo to be used anytime and anywhere. I think if that method were totally evil and useless, the browsers vendors had already disabled that method, but they didn't.

In Chrome and Opera, the resizeTo method is available just in popups, and in Firefox users can disable it manually. I'm sure that one should be very careful when using the method. But I believe this method can be useful in some case.