I'd often assume this is an indicator of a weak program, but our numbers are good, we're earning plenty of trophies and admin/community is happy with us.
Our typical DM auditions go like this:
Anyone who wants to be a leader of any sort goes through the audition process. Top score decides if they want to be drum major. If not, we go to second score. In my 7 years, the top score has never said "no" but we always had 3 or 4 auditioning.
I'm open to changing the entire process.