You want your content creation window (graphics, audio, film, 3d) to be as big as possible. You want your tool window to be as dedicated and predictable as possible. Not that I like the program, but the Gimp’s window structure makes sense in that regard - and the toolbar’s dimensions can be adjusted.
3D Studio Max’s toolkit can’t be torn off the main screen to reside on a monitor somewhere else. Takes up too much screen real estate. Photoshop’s windows may move around but it doesn’t always get it right (or if the window is maximized on another monitor, things suddenly disappear. It’s not always clear if they’re “in” the window or “beyond” it.
The absolutely ridiculous version of “tearing” is of course found in Office 2000 or so where even 2-item menus can be made into miniature windowlets without organization. What you need is some kind of grouping/flock-like behavior; dragging each windowlet for a total of 20 times to the same part of the screen is, well, stupid.
For doing lots of stuff in parallel (coding + word processing + reading newsfeeds) having a monitor for each is overkill, and the grid system makes more sense.
The laptop example explained above has made for some great user interfaces - Ableton Live and Mackie Tracktion for audio production, for instance. It even plays nicely with more screens as each part of the interface can stretch.