I've had two examples of this myself. In both cases, it was because I was unhappy with existing libraries and decided to write my own. The first was a simple

I've had two examples of this myself. In both cases, it was because I was unhappy with existing libraries and decided to write my own. The first was a simple Text UI for a business application. In other words forms using a text UI instead of a GUI. Underneath it was just laying out the screen with curses, and reading the keyboard, moving between fields on the form and doing basic jobs like text, number and date entry. I don't recall why we didn't use existing libraries, but it did mean we had something to compare it to. To this day remember the end result. It was blinding fast. So fast it ran far faster on a IBM PC running MMU-less Linux that any web form you'll find today. I still have no idea what the other libraries could possibly be doing to make them so slow. If you want to get a feel for the difference in todays terms, compare vim to vscode. The other thing was a web framework. None of the other members of my team had formal programming qualifications. All of them struggled with any sort of concurrency and I found myself forever fixing race conditions in their web apps. Whenever the "run the main loop until nothing changes" nature of modern web frameworks reared it's ugly head, they were lost. So I wrote one that didn't need that loop. Instead, when you changed a property, it and everything that depended on it changed when you did the assignment, synchronously. It turned you needed so much boilerplate it was ugly to use. But again, it was fast. The first remark most people made when using a SPA based on my app was how snappy it was. Everyone touts how simple and fast their virtual DOM is, but evidently that's only in comparison to other virtual DOM's. Compare to just manipulating the real DOM once and only once for each change, they are all dog slow. Then there is the difference between a Linux Desktop and the Windows 11 desktop. While I guess it happens less often than not, Windows 11 can take seconds to respond to a mouse click. Turns out that creates a cognitive load Windows uses seem to be unaware of. They have to constantly poll the interface to verify it's read for the next click or key press. You don't notice it until you move from a Linux windowing system to Windows. Then it's jarring, for a while.