Yeah, but full of what?

From a good piece on how the film (and sensor) size we call 35mm came to dominate the mindset and marketing of photography...

The very terminology became biased. Lens focal lengths, to cope with the hodgepodge of different sensor sizes, were already being given in "35mm equivalents," to the extent that many digicam lenses were marked in equivalent focal lengths—the focal lengths in 35mm terms the FOV of which they mimicked—rather than their actual, real focal lengths. Photographers might have no idea what the FOV of a 4.3mm lens on a 1/2.3" sensor might be, but they understood the FOV of a 24mm lens on 24x36mm, so the description "24mm equivalent" was descriptive for that 4.3mm lens. "Focal length multiplier," which described an advantage, was replaced with "crop factor," which implies an adulteration from completeness—to have a crop factor, you have to be "cropping"—cutting down or limiting or curtailing—something. What? Why, 24x36mm, of course. Then, when the simple concept of "35mm size" was replaced by the brainless moniker "full frame" (brainless because all deliberate standard formats are full frame—is a 4x5-inch contact print from a negative made with a 4x5-inch camera not the full frame?), it was an unmistakable signal that bias was afoot and roving the landscape. If 24x36mm is "full" sized, then it implicitly stands to reason just from the terminology that anything bigger is too much and anything smaller falls short.