Photos are eye candy. Quite a number of people on this site are in a country where English is not their first langue and/or reading ability was a lower priority in life growing up.

When you go to a store to buy a product. Are you going to buy something that is all just giant blocks of text or something that shows what you are buying that makes it look for quality that leads you to read back of the box for more information?

It can also be a way to keep the viewer engaged and not wander off by breaking up large blocks of texts or give a visual to something that is complex.

Some people are also visual learners. Where they value something that has more photos in it than large blocks of text to be more enjoyable.There were at a time when I started quite a few tutorial about steemit floating around that were more or less giant illustrative images. They were targeted at certain demographic on Steemit and those people earned a nice reward for creating them that way.

Now the issue I think lies when people are just spamming out 10 posts a day with a single image in each of them. Then buying upvotes for them. Without much of a purpose other than financial reward. it's hard to define anything as having value in that format. Those kinds of “bloggers” here end up meeting the same fate of getting massive downvotes for being spam when communities that go after such things find them.