If you've been itching to make big changes to your roster, a proper sample size is necessary to assess where your players stand. Three weeks won't tell the whole story, but it's enough of a snapshot to at least make changes to your personal depth chart.
Aaron Rodgers has been good but not great in the first month of the season, so if you drafted him to carry your team, expectations may need to be adjusted. The same could be said for Russell Wilson, although his returns have been disappointing and it's hard to see him making it back into the top-five-fantasy-quarterback conversation on such a flawed team.