I think much of the intellectual complexity surrounding the perception of the difficulty of knowledge work stems from comparisons to physical labor, especially factory work and field work.

The idea being that work is drudgery, and that basic fact is what justifies being paid for it. There's no doubt a bit of puritan ideology leaking into such concepts, the idea that benefit must be paid for in pain.

However, this comparison is inapt and leads to many erroneous conclusions. First of all, valuable work need not be synonymous with drudgery. Many skilled craftspersons and artisans are capable of doing incredibly valuable work with fairly small expenditures of hard labor or time due to their hard to acquire expertise and subject specific wisdom. That doesn't mean such people can't be or aren't typically hard workers, but sometimes they don't have to be in order to make a good living. And there's nothing particularly wrong with that. The work of, say, an optometrist is in some respects vastly "easier" than the work of a field hand in a sugar cane plantation, but that doesn't undervalue that work, optometry requires a lot of specialized knowledge that is difficult to acquire.

One of the biggest problems here is the notion that the basic conditions of knowledge work are less strenuous than manual labor. Sitting at a desk in a climate controlled office generally compares very favorably with, say, digging a ditch with a shovel in the hot sun. This leads people to the idea that in order to be worthwhile knowledge work should be strenuous in some way. And typically that involves working extra hours (60 or 80 hours weeks), sinking time into boring activities, or putting up with stress.

However, in reality these things don't translate into increased productivity, in fact they typically diminish productivity substantially. Moreover, long-term exposure to stress is extremely bad for an individual's physical and mental health, imposing a toll that can be significantly more damaging even than prolonged manual labor.

Again, there is the idea that stress is justified, that putting up with bullshit like office politics or death march conditions are the price that must be paid to allow people to make six figure incomes from just sitting at computers and typing all day.

But these things are just sideshows. The true, underlying value of knowledge work lies in the collaboration of many folks with extensive and specialized knowledge toward the goal of solving problems. "Hard work" may be required at times but it doesn't have to look anything like 80 hour weeks, or stress, or repetitive tasks, or backbreaking manual labor. It's possible for knowledge workers to work hard by only putting in 4 hours a week and going home to their lives and families happy, content, and unstressed.

Knowledge work isn't factory work. It's not linear, the way to increase output is not to increase input labor. Instead, the way to increase output is to stack as many compounding effects on top of each other as possible. Factory work is additive, knowledge work, when done correctly, is exponential. And it's finding the right conditions to enable knowledge workers to create and stack those exponential effects better which blows away any linear effects.

Imagine 3 software teams. The first team works 80 hrs/week building a product, every month they churn out another new feature. The second team works 40 hrs/week, every 2 months they produce a new feature. The third team works 40 hrs/week, and every month they make their product faster, more reliable, more usable, and ensure that the core systems are highly extensible; and every once in a while they will add a feature or change a feature with the criterion that it must be valuable to end-users, work extremely well, and not degrade performance, reliability, or usability. Which team would you bet on to win in the market? Which team "works harder"? Which team is more likely to be able to retain workers?