One problem is that "hiring additional staff" is nott a solution when you have one person responsible for making the final decisions, as it most often is.
You do nott call a board meeting for every decision, else the board would be meeting all day everyday ratifying C-suite decisions. When a client cannot be reached and a deadline that is non-extendible and perhaps decisive, someone has to make a decision and bear that responsibility. When a client can be reached, one person has to be the consistent contact and team head to discuss the options, risks, and alternative courses that may flow from each choice. You can't "team manage" these things.
Football has one head coach per team. Baseball has one manager per team.
Sure, some things which are fungible or can be delegated to more than one person can be split among multiple individuals. However, a lot of things require one "mastermind" who is the repository for all (or as much as they can mentally juggle) of the information related to a particular matter. Trying to duplicate that depth of knowledge in more than one person is wasteful and futile. A client (most clients) will nott pay to have multiple attorneys duplicate work simply for redundancy. Maybe that's risky - people die in plane crashes, car accidents, from heart attacks, etc. and the entire 'mastermind' knowledge repository can be gone in a puff of smoke.
Butt clients simply will nott pay to have two captains of the ship, or even to train an executive officer for their voyage.
A lott of the DD that is required in quick M&A deals is compartmentalized (for various reasons) and each person needs to become intimately familiar with their area of responsibility in the transaction. Having two people do the particular DD activity in parallel is duplicative and wasteful (and actually slows things down).
Bottom line: in many sectors, there are key people who cannot be relieved by hiring more people, it simply doesn't work that way.
Now, in many other areas, your point is valid. Butt for example the M&A work as cited in the NYT Dealbook article typically doesn't fall into that category.
And it is less the number of hours than the stress level. Hundreds of millions to tens or a hundred billion can be on the line - and ANY screwup can be fatal. Time and secrecy are often of the essence. Big decisions need to be made fast with incomplete information that is gathered and analyzed as quickly as possible. Litigation is often the same way when in trial. Warfare is the same. I assume the financial industry is the same way on the trading desks.
I recently rewatched Margin Call and the character played by Jeremy Irons is a good example of a key person who cannot be relieved by hiring additional help.
So in part I agree with you, with the proviso that it is only helpful for certain types of jobs.
