This is from the Judges Screen on the download page:
Forcing Open a door 18+ (+/-4 per point of STR mod.)
Detect a Secret Door 18+ (Elves 14+)
Listening at a Door 18+ (Demi-humans 14+)
Spotting a Trap 18+ (Dwarves 14+)
If I want to improve Detect Secret Door, I would need to be able to get the Alertness Proficiency (which some classes like Cleric can not).
If I want to get better at Spotting a Trap, I would need to be able to get the Trap Finding Proficiency (which only the "thief" types can get).
So...if I make a fighter for example, there is no way for him to ever get better at finding traps.
Also, my Thief can get a little better by taking the Trap Finding - getting a +2 - otherwise they would improve in it as they level up.
I guess I would question why others could never get better at finding traps - though I suppose "class protection" is part of the history of this type of game.
In any case, I hope I'm starting to get the Proficiency stuff.