Why do you think it's rare to find anyone over 45 in a sales position there vs. what you may have found five years ago? Is it because people over 45 suck at ad sales? Is it because they were all smart enough to get out before the company started going downhill?
Did they retire on the kick ass compensation they'd already banked - all of them? Did the company slowly restock them with folks under age 30 being paid less? If you've been around long enough, judge for yourself how much each factor has contributed. Take a look at who is selling now.