I think there is something fundamentally ancient about it, like how young women braid each others hair and probably been doing it since year one of humanity's existence. Maybe we need others to get things done. Maybe the man would jumpstart his passion if someone shared his thing for restoration.
I dont really know.
I may have done many things in life that I perceive to be valuable for our family, but nothing earned me as many 'points' with Mrs. as did the act of just sucking it up and cleaning the entire garage one day.
I think there is a lot of truth to this actually. Admittedly I'm a little sleep deprived right now in that way that leads you reading a statement and feeling it is incredibly profound in a way you might not otherwise... but still I think you are really onto something.
Working with someone smooths out the edges well when things go poorly (if something goes wrong and you are alone it is easier to be grumpy about it than if you have someone with you to say "oh well, we can do X instead" or "It doesn't really matter"), they make the work feel seen and therefore feel more valuable. I can enjoy cooking for (and especially with my partner) but I can never be bothered to really cook for myself, even if I'd enjoy the meal more in the end it doesn't feel worth the time and energy investment when I could just slap together a sandwich or something.
This extends to hobby projects as well in a big way, perhaps even more. Sure I could spend hours painting a picture and have people say "wow, that's impressive" (this is just an example, I can't actually paint), but it feels hard to justify when I have other things I might need to do. If someone else is working on the same thing with you it makes you feel like you are investing that time in them, which is inherently fulfilling.
Even in your example of you helping your friend, once they've accepted you are helping they will feel like every bit of work they do will make your life easier. It's less intense but they will still feel like they are contributing to your efforts in someway, or at least like they are working towards a mutual goal instead of something kind of isolated.
https://www.wired.com/story/to-do-apps-failed-productivity-t...
https://news.ycombinator.com/item?id=28010716
And yes, there's a lot there that resonated strongly with me.
The cars-under-tarps anecdote is an excellent one. As life goes on, one accumulates an ever-growing list of gates which have closed irrevocably behind one. The German word Torschlusspanik is a brilliant invocation of this. The English equivalent is roughly "mid-life crisis", though the German captures far more of the essence and slowly-building grief.
https://blogs.transparent.com/german/torschlusspanik/
There's saying (memory says Chinese though I'm unsure and can't locate it): a wise man is prepared to part with his possessions several times in his lifetime. That might extend to dreams and expectations as well as physical cargo.