To be fair, this grip indicator only (and still) exists when the window has a status bar. It's part of the Windows status bar design, not of the window design. Of course, many more applications used to have status bars than they do now, so that's why you see it less often.

> To be fair, this grip indicator only (and still) exists when the window has a status bar.

Here's a resizable window in Platinum that has a drag handle but does not have a status bar: https://guidebookgallery.org/pics/gui/settings/appearance/ma...

edit: I missed "Windows" in GP comment. Well let it be known that at least Platinum wasn't like this :)

What's up with that, anyway? Statusbars are great. They are one of the most useful parts of the window.