When I was in middle school, we had to do them for some kind of annual fitness test. At the time I wasn't a runner yet and, though I played a lot of sports and we were much more active than kids today, I was a total non-athlete. I smoked the entire class including the top athletes in my grade, with 8 or 9. It was strictly because I was in decent shape and super light weight (probably 90 pounds at the most).
As a high school athlete, where I was a 5'7 105 lb 4:20 miler, I think my PR was 13. A year or two later in college I would do three sets of them to exhaustion and that was usually something like 12, 10, 9 with a few minutes rest in between. I wasn't getting any better at them (could not break 13) despite doing them all the time, but I think my running was eating all my muscle away.
Around 40 years old and 150 lbs, and out of shape, I could only do 3 despite being a lot stronger in my arms and body. Now I'm just over 50 and I doubt I could do more than 1, but I weigh 160. Pullups feel like the absolute hardest thing in the world at this weight even though my arms are much stronger than when I was in my 20s. It's all about having a light body. I'm sure if I keep working out and drop 40 lbs I could do 10 pullups again (hopefully we'll see in 6-12 months as I've just started working out again).
Distance runners who are really fit and reasonably well trained in the arms will probably come in around the 10-15 range. If you quit distance running and become a basic gym bro before you just get fat, you can probably get it up to the 20-30 range without too much difficulty. Most people don't do the specific exercises necessary to be good at this.