The top three picks are the best indicators of draft success for each team. When pundits and analyst go back and grade various teams' draft success, they look at the top three picks to identify how well the team drafted that year.
To be successful a team has to be ready for whatever scenario that comes their way on draft day. With the Cowboys selecting at the back end of the first round, they will need to be able to act quickly on their feet because there are numerous scenarios that they must be ready for.