Window and Tab Spawning Sites

Why do sites feel compelled to spawn a new tab or window for every link you click on? Its a pain in the ass to have to keep shutting down previous tabs when they do this. Is this some way to game advertising or do they do it because they are just so very, very proud of their homepages that they want to keep them loaded up on your browser forever and ever.

This spawning problem is less annoying then the sites that hijack browsers altogether and then see fit to make them as large as possible, difficult to close and overload processors with garbage media embedded in the page. Actually, those sites are waaaay more annoying.

But window and tab spawning is stupid too.

I guess I'm on a stupid and pointless kick these days.

[Update: To clarify my point of annoyance! Sites that open a new window with each click annoy me. Either a new window or a tab. What this means is that, if you go four pages deep into the site, you've got five windows or new tabs. Unlike most sites where the clicked link opens up in the same window or you can right click and choose to open one in a new tab or window.]