This is similar to asking why Unity for a 2D game when something like SDL/Pygame/Love2D will work... sure it will and probably will be much cleaner for smaller,

This is similar to asking why Unity for a 2D game when something like SDL/Pygame/Love2D will work... sure it will and probably will be much cleaner for smaller, simpler things but I couldn't phantom building something with a lot of interactivity, popups, drag and drops, interaction, etc. with just HTMX and Alpine, and you get a massive ecosystem of UI libraries with premade theming, etc. Plus now React has NextJS which also gives you backend and SSR capabilities into one cohesive solution. htmx looks really cool to me and I probably would chose it if I were to build something like Hacker News with little interactivity where I just need to show a few things reactively, but it's just not the right tool for all applications. Even if you build something simple and small you can use a small subset of React without any complex frameworks or libraries, just as a single library, and it will work fine and won't be too complex. Disclaimer I have not used React extensively although I did work at my dayjob with Vue which is very similar.