I can't be the only person who finds browser default behavior more intuitive and usable in general.
Why does "UX" so often mean mouse-heavy and always favor the beginner over the power-user.
I'd say apps skew towards mouse-heavy because controls are on-screen and therefore discoverable. It takes a good deal of product-market fit before you can count on your users knowing/caring enough about your app to remember keyboard shortcuts.
Most apps are grown by adding users, so optimizing for the new user is more important to the business until a certain level of maturity and market saturation is reached.
Applications with a dedicated professional user base can go deeper into power-user territory sooner since they can charge more per user, and new users expect there to be a learning curve.