2. Faster than shrinking a photo I took, a screenshot is almost always smaller.
3. I clean out captions with no meaning for my post, without opening an image editor.
4. I save tweets and excerpts of README files that say all that I need.
5. I put windows (typically images) side by side for a quick montage or comparison without opening GIMP. (snap)
6. I save screens with account balances for reference, and pretty much anything from Apple's App Store that doesn't allow copying, or listing. Some JavaScript (sc**d?) disables copying, so I screenshot or turn off JS (YMMV with that)
7. I snap images for my recipe manager that are hard to save, ( in some JavaScript flip book), webp (growl) format, or are movies.
Almost never full-screen, nor web page > 1 screen.
I use an app that lets me select an area, and saves snaps, and also lets me copy/drag the snap.
Usually for pasting into Slack to discuss. Sometimes to paste into Onenote for docs. Occasionally for blog posts.