An opposing view seems to come from people who have both large desks, and keyboard trays. In those arrangements, there is plenty of room for a full-size keyboard. And if your software uses a lot of dedicated keyboard shortcuts, a larger keyboard can be incredibly powerful.
I do not have a large desk, personally. Indeed, I took this photo earlier.
I actually came back to this thread to say something. I switched over to my Model F to make a point to myself, but I also discovered that it's a space saver for me. I typically use a full size Model M, and with that, I sacrifice all spare desk space. Indeed, with my monitors, I already have one hanging off the side of the desk to the right and it's taking up a solid 25% of the mousepad as well. I just don't have the space people seem to.
If I had 3 more inches in any direction, a full size would be great with no compromises. I don't, so I'm really enjoying the fact that I'm not shoving my keyboard into a corner and I'm not cramping my mouse style right now. However, I highly, highly, highly doubt that most of the people with the 75% or smaller keyboards are using a desk smaller than my own. So, to me, unless your monitor is hanging off the desk and sitting on your mousepad, you don't need the extra space from a smaller keyboard.
Anyway, again, I have been enjoying this keyboard, which has been the ideal space saving model for me lately. Here are some reasons:
1. It's got long feet so it goes over my monitor stand in the middle, freeing up desk space.
2. It doesn't have the numpad and nav cluster separated, so I save horizontal space that way.
3. The function keys are on the left, so I can type out in front of me and not smash the mouse.
4. Uh...
Anyway, I've discovered that I've had to make a few compromises that the compact form factor people have to, that is, having a "function layer" for certain keys. I mean I have to press numlock in order to type on the numpad, which is easy, since I typically use it for longish bursts infrequently, that corresponds to my usage. And, considering that was its original design, it's probably fairly normal for it to work like that for people.
I like it.
Now, someone said that people like things small and cute. I think that's true. It's a fashion choice. Look at the mechanical keyboards subreddit. It's essentially a keyboard photography forum where people make their keyboards look as small and as cutesy as possible. That, to me, is what is driving this, not function. They're just rationalizing it to themselves. I mean, come on. You bought a pink keyboard with apple blossoms and a $100 ****ing cable with a pink aviator connection to put on your anime deskmat because you think it looks cool, not because it "saves space."