I'm not exactly sure what kind of world he lives in. But in my world, someone has to get the kids to school, do the dishes, take out the garbage, pay the bills. There are things that have to be done daily, weekly or monthly that will never, ever be the One Thing that I'm passionate about on any given day. I can come up with all kinds of great metaphors for doing my taxes but tax prep will never be my One Thing. If I followed his suggestion, I might be a little happier but I would get even less done than I already do (which would be amazing considering how little I actually get done most days).
I know that even though he didn't specifically say it, I'm sure he understands that the One Thing system won't work for everyone. (He does say you can keep a list of routine items that you can look at once a day if you "don't feel safe" without it but that's sort of insulting to people, like me, who need reminders to pay bills and stuff). Honestly, I don't think I know any normal person that could successfully use that system. Maybe I'm just surrounded by people who, like me, have relatively complicated lives (or short attention spans and an inability to remember to do boring but necessary stuff). And so the idea of totally doing away with to-do lists is terrifying and not particularly helpful.
Because I don't want to be the kind of person who just shoots down someone else's ideas without offering something of my own, here's my idea for improving on Leo's One Thing. I call it One Thing Plus. What if we kept our to-do lists but made sure to make room in each day for our One Thing? It would be great to know that when you wake up in the morning, you pick One Thing that you're excited about that day and you get to spend some time working on it. Because it's already on your list. And maybe it makes the rest of your list easier to get through if you take some time to do something you're passionate about.
I'd love to hear about your systems and whether you make time for your passions in your day to day life.