When you have your portrait taken by a professional photographer, you expect a different result than when the DMV takes your driver's license picture. The DMV actually has specific rules about how your driver's license picture must be taken. Driver's license pictures are for technical purposes, for identification. Most people have a professional portrait taken for some other reason. For those other reasons, professional publicity, weddings, graduations, family keepsake, etc., we generally want a picture that's more flattering, more interesting, with a specific theme or message, maybe even one that hides our little flaws while emphasizing what we see as our stengths. The DMV wants a picture that clearly identifies the subject. We generally want a portrait that makes us look attractive or interesting or professional, whatever.
Next time your at the Post Office standing in line while the person in front of you mails 35 packages each of which has to be weighed, look over at the wall where the wanted posters are. You'll probably see someone you know. Well, probably not. But, you'll probably see someone who looks a lot like someone you know. Despite the fact that we all strive for individuality, style our hair, grow a beard, new glasses, whatever, when you strip it all back to a very technical mug shot, what you basically discover is that people look a lot alike. There's only about four or five basic face shapes. Just about everyone's got two eyes, a nose, a mouth. The basic features are the same
The knife photographer finds the same thing is true. After a while, knives all start to look the same in thos those technical, what I call "knife mug shot", pictures. So, you start to search for ways to make the picture more interesting.
Portrait photographers often have their subject turn and take the picture at some angle. My avatar is done that way. It makes it more interesting than a flat, straight-on head-shot. It makes it look like less of a mug shot.
The three-dimensional picture is exciting. It's attention-getting. It makes your product stand out. And that's why many manufacturer's prefer them for advertising.