You don’t need to support a ton of complex stuff, but if an rgb image format doesn’t then it should just have a version marker and the spec can simply say “the rgb data represents sRGB colors”.

Just like e.g. some compilers don’t support a lot of source file encodings but their non-support consists of clearly stating that a source file is UTF-8.

Note that this requirement is only for an image exchange format. A raw-er image format used internally in e.g a game doesn’t need it as badly.

But in an exchange format every user needs to know whether the image data is sRGB or Adobe. Because the reader didn’t encode the data.