Precisely because it can be used to sprinkle JS functionality :)

Vue and Svelte are great but adopting them means that you are using Rails as just a backend. For the vast majority of apps, the Rails default stack works really well.

For most apps/sites something like Stimulus, htmlx, etc are good enough, also all JS frameworks comes with complexity, now you need a bundler, eslint, prettier, postcss, etc. I can appreciate the simplicity of relying purely on Rails ecosystem or at least very minimum JS that does not require a bundler.