More clarification on updating Objects in state

here in the current beta docs of updating objects in react, we are just told to treat objects as read only and never try to mutate them but what are the exact tradeoffs if we try to mutate the existing state Object, i am quite confused and may be this requires a brief explanation

Like i have a sandbox below where it tries to just mutate the object directly and it works as expected

https://codesandbox.io/s/kind-poincare-k4g8uh?file=/App.js

从链接的 beta 文档页面开始，更新 state 中的对象，并查看展示直接 mutation 的链接 CodeSandbox 示例。明确 mutation 现有 state 对象与将其视为只读之间的确切权衡，以便页面解释为什么推荐的方法很重要，同时说明这个看起来能够运行的示例。