Beyond a certain point, more hours becomes more hours for the sake of there being more hours, not necessarily because they are beneficial to one's training. Plenty of European countries limit resident hours to 45/week, and their health outcomes aren't exactly suffering because of it. If the program's graduates have a decent board pass rate, they're probably being trained just fine.
More hours becomes more hours when you're cheap labor. Never underestimate the profit incentive, it always plays a role. Residents are a hell of a lot cheaper than hiring more hospitalists. You don't think your preceptors are actually gonna pick up the slack, do you? Is there actually THAT much more learning that goes on when a 60 hr/week turns in to an 80 hr/week? Possibly.
There's a lot of politics as to why residents have the hours that they do. It is our version of basic training. There is hazing. There are egos. There's definitely a profit motive. Certainly an "I went through it and you do too" attitude. You are essentially powerless as the directors and preceptors can at any time and almost any reason end your medical career whenever they so choose (and they know this). There's more but these are just off the top of my head.
It's a double edged sword and we must walk a very fine line. The more we try to diminish the rigorous nature of our training and the fewer procedures we do, the more we'll be equated to mid level providers (if we're not already there in the eyes of the beancounters.) Beware of ANYTHING that makes you in any way appear similar to your fellow "practitioner" who can be had at less than half the cost.
Does it suck? Oh God yes, and there are some places that are worse than others but from what I've seen there are similar aspects seen at most programs. What's the reward? Well, lots.
Patients will often consider you a part of their family
Helping those who will listen to hopefully live the most fulfilling and longest life possible
Almost guaranteed to be a top 5% earner
GREAT work/life balance after dues are paid
Ability to leave and find an even better job pretty quickly if you so choose