It's a good way to think about lots of things. It's Pareto efficiency. The 80/20 rule

20% of your effort gets you 80% of the way. But most of your time is spent getting that last 20%. People often don't realize that this is fractal like in nature, as it draws from the power distribution. So of that 20% you still have left, the same holds true. 20% of your time (20% * 80% = 16% -> 36%) to get 80% (80% * 20% => 96%) again and again. The 80/20 numbers aren't actually realistic (or constant) but it's a decent guide.

It's also something tech has been struggling with lately. Move fast and break things is a great way to get most of the way there. But you also left a wake of destruction and tabled a million little things along the way. Someone needs to go back and clean things up. Someone needs to revisit those tabled things. While each thing might be little, we solve big problems by breaking them down into little ones. So each big problem is a sum of many little ones, meaning they shouldn't be quickly dismissed. And like the 9's analogy, 99.9% of the time is still 9hrs of downtime a year. It is still 1e6 cases out of 1e9. A million cases is not a small problem. Scale is great and has made our field amazing, but it is a double edged sword.

I think it's also something people struggle with. It's very easy to become above average, or even well above average at something. Just trying will often get you above average. It can make you feel like you know way more but the trap is that while in some domains above average is not far from mastery in other domains above average is closer to no skill than it is to mastery. Like how having $100m puts your wealth closer to a homeless person than a billionaire. At $100m you feel way closer to the billionaire because you're much further up than the person with nothing but the curve is exponential.

https://youtu.be/bpiu8UtQ-6E?si=ogmfFPbmLICoMvr3

"I'm closer to LeBron than you are to me."