If someone uses an AI generated image, the alternative is almost always going to be a CC-licensed or otherwise free image. Almost no one is paying for photography for a non-commercial blog post.

The OP mentioned technical blogs, which are commercial a lot of the time. I should know, I've written a lot of them.

They're "commercial" often but that doesn't mean someone necessarily has a budget (other than being paid a salary) to do them.

In many cases, I think it's far more likely that an image would not be included if it required paying an artist. It could be stock art or photos almost as easily and with that, not many people are getting paid for it.

how is their labor any more valuable than thousands of other occupations that were replaced or made redundant by technology already?

besides, all those shitty blogs were using shitty stock images and bland twitter memes. budding artists generate revenue primarily by drawing risque pictures (primarily of someone else's copyright protected characters, but no one likes when this is brought up)