Online dating is very visual. People judge you by what they see on paper, which in essence, is your dating profile. In real life, your bald-headed friends are able to show a lot of their personality to women which could easily attract said women to them.
On a dating site, they only have their pics and a bio for the most part. Since, online dating can be very superficial, women quickly judge these men for being bald or short.
These are the same women who would have given these men a chance if they had met them in real life instead and gotten to know them as a person.
Superficiality is one of the negatives about online dating. It is not so much that online dating causes it. It is just that online dating illuminates the innate superficiality that exists in most human beings.
The good news is that the bald and short guys who stick it out ultimately get matches on dating sites. They just have to be a little bit more patient and persevering than the guys who have the genetic advantages of having a full head of hair and height.