A tiny video camera can produce real 1080p images, and they may be pretty good. However, the quality of the lens matters a great deal, as do other factors, such as lighting and contrast of the image being captured, etc.
Effectively, whether a camera is 1080p or 720p is analogous to telling you something (but not everything*) about the film in a film camera, and that is part of the question of how good the resulting images will be. So it is not simply a question of "marketing." But there are many other factors affecting the end result, and so you should not expect be able to capture the very best images with a camera like those you mention.
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*It is like telling you something about the film grain and size of the film, but does not tell you any other quality of the film.