Sure, the Intermediate and Advanced Master divisions are about the same skill set, but there is more to the big picture. It's all about the tourney experience, right?
The Advanced Master division players are most likely seasoned disc golfers that lack the skills to compete in the Advanced Open division, but they know the rules, have proper etiquette, and are playing to have fun and to curb their competitive drive at a course that has been groomed for the tourney.
The Intermediate division players on the other hand, are mainly new to the competitive scene/sport and are still learning the game (skills and etiquette) and have the potential to play in the Advanced division once their game improves (not the case for the majority of the Masters division players).
Personally, I was looking forward the time when I turned 40 and could start to play in the Pro Masters division, but now after 12+ years of playing and promoting the sport of disc golf (not to mention a family and real job), I have realized and know that I don't have the time or mind set that it takes to compete at the professional level and will most likely stay an amatuer player for life.
I turned 40 this year, so watch out Advanced Masters players.