Because we want the application to have a modern look and feel, and this Python developer has a genuine desire to start learning about modern web technologies.
you think that e.g. Telegram or MauiKit apps don't look modern ?
(Also, while React is my go to web framework because I’ve learned it well from necessity at $DAYJOB, it’s not particularly modern.)
As I see it, people with genuine desire to learn don't see details such as "number of dependencies" or "linters" as impediments to anything at all.