This applies more to teachers than to anyone else, but clip art (especially black line clip art) can´t be beat when it comes to using images that are going to be photocopied. It creates a much cleaner look than a photo. While there is much talk of going digital, the reality is that most of the world still is using paper for teaching . . . and a lot of it, not because we aren´t open to the digital world, but many times not all students have access.
Why is it that every time Microsoft make another edition of their software it makes it harder and harder to use. Seriously frustrated. Clipart was so darn useful. I was always ungrouping it to pull apart and use just some little images or to recolour to match my document / presentation. now I have to go and try and completely redraw things. This is a complete waste of time. Microsoft, you continue to be morons. Just once, I'd like to see an upgrade that actually added value and didn't make it harder for people to use. User UNfriendly. Seriously considering heading back to an earlier version of PowerPoint just so I can get that feature back.
This is TERRIBLE! Besides being able to edit vector images like Will mentioned (which is important for those of us who don't have graphic artists available to create custom images or the budget or time to buy that service ad hoc), you could also search for style "families" (different graphics that were all in the same style). There was a huge range of files and styles in the collection and it was much faster to find what you need than to do a Bing search. Plus, you knew that everything there was free and free to use, without having to worry about CC license issues.