I don’t think that this is obvious for solutions.
Usually when you quote something, you quote an excerpt of another
post. People that want to read the context could click on the downward
arrow to expand the quote.
When you mark a post as solution, you usually regard the whole post as
the solution. Apart from the fact that you cannot mark an excerpt of a
post as solution, you always end up with a solution without images.
I don’t see a reason why a solution should only contain the whole text
of a post, but should not contain any visual content.