Investment banking is all about dealing with other people's money and the customers usually are pretty demanding when it's well, about their money. From what I hear from my investment banker friends a lot of the day is spent socializing and going on client meetings, lunches, dinners to satisfy the relationship and then usually back to the office to do the 'actual work'. It's a lot of hard work but that's why these guys get paid $200-300k soon after joining.
Investment banking is about helping companies raise equity, debt and engage in M&A, not dealing with other people's money (maybe your friends were in wealth or asset management, which sometimes sit within the investment bank?)
Having been a junior banker myself (and with friends at most banks across wall street) I can tell you that virtually no one is being taken to events or spending days socializing as an intern, let alone as an analyst or associate. You spend your days preparing pitchbooks (to pitch companies on why you should be the bank representing them), building financial models and putting together management presentations (in addition to any one-off requests your senior people or the client have). Can go into more detail but it's covered pretty well in comments above.
(Also there's no such thing as shadowing a manager in investment banking - just doesn't exist. There are mentorship programs that the banks run, but the vast majority of the time they consist of getting coffee at most once a month)
I think your response is way too literal. junior people routinely sit (quitely) in higher-level meetings so mid level people don't need to regurgitate stuff. They also spend alot of time developing lower-level social networks so they can function and get stuff done (doesn't need to be socializing with ceo). and all investment banks are (essentially) dealing with other peoples money unless they are prop trading, which is of course not how actual ipos are financed. etc.
Even if they adhere to this new rule that's still 17-hour days. Does not sound balanced at all to me. I assume these guys work the weekends so it's a 119-hour workweek.