A lot of people use Astroglide, as it is easy to find. Also, a lot of younger doctors feel cool suggesting Astroglide instead of staid old KY, like their fathers did. Really.
We used to use it, before I found lubes we realized were a lot better for our needs.
Also, when people are just starting out reviewing, they may not have a lot of sex toys, but they probably have a bottle of Astroglide lying around to review.
One of my first few reviews was Astroglide glycerin and paraben free (Green Cap) and I reviewed it because it was the first lube that didn't give me infections. Like I said, we've found much better lubes lately, that we like a lot more, but it was one of the first things I reviewed, after my beloved Wahl.