They make progress, but they also have no deadlines, commitments, oe bankruptcy-threatening budget pressure, and not in the same league from a perspective of personal return on investment . It's a different model that can't be adopted by all.

Although in the case of most big OSS projects, a lot of the work is done by teams, many of which are co-located and/or have communication channels outside of IRC and email. In addition, in-person get-togethers are fairly common with many of the big projects.