You're probably friends with several people in that top 20% because they know a lot of people. The average number of friends your friends have including the outliers is going to be higher than the number of friends you have.
If you think about it, this is not far from saying that: if you know a distribution is non homogenous with a limited number of elements skewed - like say a normal distribution - and pick an element at random, it is more likely to be average than exceptional which is pretty trivial when you think about it.
A lot of dismissals miss this in talk about super popular celebrities. It just requires that some people have more friends than other people. The people who have more friends are more likely to be friends with you than the people who have fewer friends [edit: even if "more friends" means five friends and "fewer friends" means four friends.] That's it. It isn't about outliers pulling up means.