What are the disadvantages of React.js memo function?

Question

The memo function of React.js seems to me to have no disadvantages. It seems that the rendering load can be minimized because it is not affected by the state modification of the parent object, but if there is no downside, why is it not the default value for the React.js component?

import { memo } from 'react';

const App: FC<Props> = (props: Props) => {
  return (<div>...</div>);
};

export default memo(App);