It's basically a batteries not included problem. Say you create a new React app. The fact that you do is an indicator that the core tech (web tech in this case

It's basically a batteries not included problem. Say you create a new React app. The fact that you do is an indicator that the core tech (web tech in this case) does not satisfy your needs out of the box. So you grab a framework from "user land", one of many. React though is not self-contained. To even get it to build anything, it depends on various other projects that each have deep dependencies. Webpack, linters, a choice of CSS framework, etc. At this point, you app itself has zero functional dependencies. You haven't even produced a hello world, all of this stuff is needed just to get it to do anything at all. As you'll then start to build actual functionality, you'll notice that React doesn't have facilities or an opinion on the most basic of stuff. Loading data, managing forms, standardized UI, the essentials are not there. So you go for robust/popular libraries for each of those gaps, which in turn have their own dependency trees. This way even the simplest of apps require thousands of dependencies. It's not due to developers too lazy to write "leftpad". It's a tech stack issue where nothing is standardized or included out of the box.