From another thread, I think Jeff Mingay's response to Tom Doak (copied below) gets to the heart of the matter;
Quote from: Tom_Doak on November 13, 2007, 07:17:45 am
In my experience of consulting at older clubs, there is a universal fear that our suggestions (for removing trees, widening fairways to their original width, even making greens larger to bring the corner pin placements back into play) might make the course "easier" or reduce the slope rating. It's not just the good players -- nearly everybody thinks "easier" is a step backwards, or else they just don't want to be seen as wimps who need to make the course less challenging for themselves.
It has taken me a long time to perfect the explanation that some changes will make the course "easier" or "harder" but we are not trying for one or the other, we are just trying to make it more interesting and to bring back a lost nuance of the original design.
This "harder" mantra is a significant cause of the defacing of good old golf courses.
I think Robert Trent Jones' work at making a number of high-profile 1920s era courses "more difficult" for championship play, beginning in 1951 at Oakland Hills, are undoubtedly several of the most influential events in the history of golf in America.
Amazing. Fifty-six years later, the Oakland Hills hangover remains.