I’m guessing that it’s just a much harder problem. Images often contain more information but it is far less structured and refined than language.

The transformation process that occurs when people speak and write is incredibly rich and complex. Compared to images which are essentially just the outputs of cameras or screen captures — there isn’t an “intelligent” transformation process occurring.

I think images also have much higher information density than words, or at least they can. There is a reason a picture is worth 1000 words.