In a blog, real images signify you spent a lot of time creating the post, it was very important to you, and you likely made sure the details in the text were accurate.
While AI images in a blog signify low effort high volume posting where the text likely was just copied from AI without any care.
It's not just about effort though. I prefer the authors terrible doodles over AI art any day of the week.
Some of my favorite examples:
I don't think it signifies any of those things. This is all new stuff. Some people have decided to offload image-creation to machines because what they care about is the text.
This stuff you say it signifies, it says more about you than them.
The article author should have specified more closely which type of image. Stock image sites had already made generic photos and drawings cheap to include. And indeed they look cheap. The more airbrushed and high quality the cheaper it looks. If a dentist website has cheap beautiful stock nurse photos, it's less valued than real photos taken by a photographer at their location.