The people who do are a significant minority just around ~30-40%. Wouldn't be a tremendous market for ear hooks otherwise. There are thousands sold every day on some retail sites and sometimes thousands every hour if discounted. Out of the 2 dozen folks I know who have bought airpods, 8 have also bought ear hooks. That's ~33%. Anecdotal, but you can look at sell figures and the vast variety of airpod earhooks products if you don't believe me - and look at the 10k-100k product ratings.
I am surprised to hear your experience here. Many of my friends have them and only one has ever mentioned a fit issue. He bought larger tips and they now fit perfectly apparently.
Researching I can indeed see such products exist, although given Apple appear to be selling over 100 million pairs a year[0] (also surprising to me!), I suspect your estimate is inflated. Note this is over 300,000 pairs per day.
Anecdotally, I see people with Airpods daily but have not once ever seen hooks on them. Maybe there's a cultural element at play?
Sweet devices that keep falling off your ears. You need AirPod ear hooks to keep them on.