A very large number of published documents contain text only. They often look boring, and they are often written in obscure language, using mile-long sentences and cryptic technical terms, using one font only, perhaps even without headings. Such style, or lack of style, might be the one you are strongly expected to follow when writing eg scientific or technical reports, legal documents, or administrative papers. It is natural to think that such documents would benefit from a few illustrative images. (However, just adding illustration might be rather useless, if the text remains obscure and unstructured.)
It is too easy to go to the other extreme when trying to avoid the boring plain text syndrome. This is especially true on the Web, where it is relatively easy technically to add illustration, for instance by picking images from various existing collections. Many people seem to think that you can't have too many images. If they can't find a suitable image, they use an unsuitable one.
When people say that one image tells more than a thousand words, they tend to overlook the fact that what the image says might be true or false, relevant or off-topic, useful or disturbing, constructive or tasteless. (I won't bother to refute the saying by pointing out that there are images which say nothing. However, I cannot resist the temptation to remark that oddly enough the saying itself is expressed using words.)