Tom,
Some fellows were discussing this today.
Physics has a lot to do with it.
That and the fact that the spectrum has been broadened.
When 14 year olds are hitting it longer than Nicklaus in his prime, designing a golf course to serve all levels of golfers can be a difficult mission.
There seems to be a "Red Badge of Courage" known as the back or "Tiger" tees, without which, a course may not be considered as a meaningful challenge for the better player (Pro).
Whether we like it or not, length remains an inherent element, if not the critical element, in presenting a challenge. Thus, a long course must be part of the architectural equation when designing courses for today's golfers.
I can remember when courses at 6.700 presented a meaningful challenge to the best golfers in the world. Then it went to 7,000. Today it's probably closer to 7,500. Who knows what it will be in the future ? But, whatever it will be, will have to be built in order to preserve that challenge for the best players.
Then, there's another perspective.
How can you as an architect design features that will integrate with everyone's game, physical and mental, if you don't differentiate play vis a vis different sets of tees ?
Bunker placement would be a dilema if there were but one set of tees, unless, you littered the land with bunkers.
The problem with building an abundance of bunkers is that it would present an overwhelming challenge to players with less ability. It wouldn't be fun for them, it would be tortuous, certainly not the kind of course they'd seek for repeat play.
So clearly, a critical segment of the golf market would reject your design as being too penal, and survival of your creation would be in doubt.
The short answer to your question is:
Because the ruling bodies of golf allowed the distance issue to get out of control.
What was 6,700 in 1960 is equivalent to 7,500 today, and if you don't build golf courses for "today's" golfers, how would your product be received ?
The term, "pitch & putt" was always used as a derogatory phrase when describing a short course. In some ways it referenced a one dimensional course that offered little in the way of a challenge for the better player, amateur and/or pro.
"pitch & putt" courses used to be about 6,200-6,400 yards.
Today, it's probably 6,600 to 6,800 yards, so, in order to avoid that label in the minds of the retail golfer, you have to add distance, unless you've got an unusual golf course in an unusual environment, and/or lots of wind.
If you're not at 7,000+, in the golf world's eyes, you're not presenting a meaningful challenge.
It's not ego, it's not gender, it's simple physics.