If the powers that be thought about it that way they could have specified 'challenging VFR' as a requirement for that XC.
The 'powers that be' are
not experienced flight instructors, nor concerned experienced old pilots, or even government officials tasked with aviation safety, as we most probably think when considering FAR's. The powers that be are the lobbyists (just like all other forms of government) that block all proposals for increased training because of the cost of training.
Do you or anyone actually believe that a Private Pilot should have that amount of legal flying authority after only 40 hours in the air? These days? It might have been ok in the '40's, or whenever it was conceived, but not today. ...and it isn't "the FAA, in their wisdom", making these determinations, it is the lobbyists whose job is to block flight training costs.
...and as long as an 'acceptable number' of accidents occur, and as long as the public is ignorant - no change will occur.
For most folks those dual XC trips ended up being a costly relatively idle exercise.
Unfortunately, this is totally the instructor's fault.
Actually, the regulations were conceived and written very loosely, for the distinct purpose of allowing the pilot or instructor to further define the meaning and intent depending on local environment and type of aircraft.
But that was before flight training was openly available to 'the masses'.
The masses wanted specifics. How much will it cost? What is the
minimum that I can qualify in? Why do I have to do that? I'm only gonna fly a 172 on sunny days...and so on.
Lawyers took over. Flight instructors became a dime-a-dozen and lost all power to influence training and became flight school monkeys.
Anyway, it is impossible to micro-manage every student by
regulation.
That is, and has been, the intent of the instructional regulations, that the instructor should determine the specifics of the requirements, such as, if the commercial applicant is weak or inexperienced in primary pilotage/DR type navigating to and finding a grass strip,...
or navigating to and thru a Class B, or...whatever the applicant needs more training in to become a pilot who is capable of flying his/her first charter to a grass strip resort in a hidden valley, or to a major class b airport to catch a commercial flight...
But you are right. Because the students (customers) have taken control of the school, via the lobbyists who protect their commercial interests, no one wants to fly more than the minimum 2 hours and then if you can
substitute a portion of your instrument training,..why, you've just saved yourself hundreds of bucks, right?
Now, that being said, the regulations also allow a pilot to get certificated with minimum experience, and then use his/her certificate to progress at continuing training in those areas where he/she did not really get the experience needed for the job or location or equipment. If everyone did this, the regs, as they were once written, were sufficient.