Every industry does the same thing
This is absolutely not true. The vast majority of industry trade shows look quite professional. A small minority of industries that attract people with developmental problems (automobiles, guns, and games) don't.
Actually, those women who sell pharmaceuticals to doctors or telecom services to engineers kinda disprove your theory that its not an industry wide issue.
Public relation groups and special interest groups are full of ex-cheerleaders and attractive men and women.
Not saying its right, just saying its not just E3 and Boat/Car shows.