@MonaApp Because the alt-text adds context to the image and vice-versa. For instance, if the alt-text describes a specific detail of the image, it is kind of absurd to be two actions away from being able to actually view that detail (and then two more actions away from being able to finish reading the alt-text). The image and its description are the same content, and should have the option to display together.
(Not everyone who needs/uses alt-text is 100% blind, fwiw.)