Say we have component:

let Component = (props)=><div>Hi</div>;

I have sometimes come across code where someone calls a react component as function in render:

 const App = () => (
     <div> {Component()} </div>
 )

vs rendering it as element

 const App = () => (
     <div> <Component/> </div>
 )

In react hooks, what are possible drawbacks of calling component as function?

There is similar question but it is not specifically targeted at hooks - also that question is more about performance.