I think your emphasis on work is just a mistake. (Even though, indeed, my children have jobs in which their bosses do praise their constant questioning. Very much so. That depends on the job, of course, it's clear.) We don't bring up children primarily for work, do we?
The world can indeed be harsh. But, well, there are ways of dealing with that. I, my partner, my children, my grandchildren, we are all pretty happy, more-or-less appropriately fulfilled as human beings, if you like, in despite of the harshness of the world. How so? Lots of reasons.
[Of course luck comes into it. But we haven't been lucky all the time. Let's not get into hardships; there have been some.]
I'll take up your cavil about questions. I always tried to answer my children's questions; they do likewise with their children. Result? - Grown-ups with an appreciation of the world they inhabit. (And other things too, but I decided not to boast too much.)
I do think it's good for our children if we do that, so in a sense yes it is our duty as parents to do so. But I can also report that answering children's questions is fun. (You need lots of time, of course, that takes a bit of working-out, I know.)
Why? (Kids always go through a Why? phase, you might have noticed.) I'm not really sure, but I think it's probably connected with love, given and received, and also with evolutionary-determined species curiosity. Why? - Why what? (Sometimes a question gets another question as answer. But not always ...) Why species curiosity? - It's interesting, isn't it, how evolutionarily-determined aspects of our nature become imbued with value. No? How might that be so? ... Oh, and so on and so forth.
Do you get the idea?
Or, perhaps, 'Why do I have to go to school?' ... 'To learn interesting things and to meet friends of your own age.' ... Why? ... 'So you'll become an interesting person.' (Not, notice, '... So you'll get a good job.' ... 'That's a really bad reason. Isn't it?') ... 'Why?' ... 'Because it's easier to be happy if you're interesting.' ... 'Why?' ... 'Interesting question. Probably just something to do with being a human being.' ... 'Why?' ... 'Well, there's something called 'evolution' and that connects somehow with how we value and care about things - like how you love your mum and dad ...'
'But I'm bored!' 'Well, sometimes it's necessary to be bored, so you can get something you want. But often if you feel bored and you just think a bit more about what you're doing and why, you'll get interested and won't be bored any more. Try it and see.'
There you go. Try it and see.
[Children actually ask really interesting questions, given half a chance. From a grandson recently (eight-year-old): 'Why do we have a word "now"? There is no "now", is there? By the time you've even said it, it's not "now" any more, is it? It's "then", isn't it?'. Or from a granddaughter (ten): 'When you think of a world without you in it, does it make you feel strange? I mean when I try to think of a world without me, I feel a bit kind of dizzy inside. Do you feel that? Why, do you think? What is that feeling?]
Parenting is hard work, time-consuming. But ultimately fulfilling when done right. Doing it right involves - in my opinion - always trying to answer children's questions.
That's a bit of a rambling post. Probably a bit self-indulgent. And too long. Sorry.
But, anyway, to finish, let me just reiterate that you should never slap or smack a child. Really. Just don't. It's wrong.