David,
There are a few ways to answer this question. Some profiles are "orphans", which means that someone created the profile and then abandoned it. You can usually "adopt" the profile if that is the case.
Since this is a collaborative tree, you can improve the profiles of your ancestors, even if you don't manage them -- as long as the profile isn't locked by its current manager. Many profiles in Wikitree need improvement -- source additions, biographies, etc., and most often a descendant will care the most about accuracy and reaching out to connect with more cousins.
I think David Selman covered the rest of this topic with his post -- but ask again if you still have questions.
Reba