Players want 1) money and 2) exposure for their brand (themselves).
Several teams provide #1, but only 2-3 teams every year provide #2 without actually winning a Super Bowl.
In other words, the Cowboys are the safe bet because even if the Cowboys fail to go deep in the playoffs, they will be talked about in great detail all season by the media.
That said, the only reason the Cowboys brand has remained popular despite 28+ years of failures is because the previous Super Bowl generations of fans are still alive and supporting the team.
As that generation atrophies in the coming years, the Cowboys brand will fade without Super Bowl successes.