Question: For instance:

```
function getUserInput(input: any): any {
    return input
}

```

It seems silly to declare "anything can be returned". What's the purpose?

Answer: 
It is useful for the lazy and the ignorant.

But don't take this as a rant !

Sometimes you (or your client / boss) "need" to be *lazy* on typing. You need to quickly write something when the actual type is too complicated, as already noted in artem's answer.

It could allow flexibility in coding. (though it could lead to a poor code base eventually)

Also, you may very well be completely *ignorant* of the actual return type of some API call or javascript function that is a black box for you. Maybe it constructs dynamically an object and has dozens of possible return structures.

For instance : how would you type the result of `eval` function if the (sanitized) input could be a variety of json expressions, or a number, or a string etc?

When you start to write `object | number | string | boolean | null`, you want to write `any` instead, for readability.

But of course, you should try to avoid this as much as possible, it is considered bad practice. 

Anyway, I think it would complicate things to miss this language feature in certain real-world scenarios.

EDIT : and I nearly forgot, but I think TypeScript *must* have this feature or a similar one as per its specification : every JavaScript code is supposed to be "valid" TypeScript (the compiler will gladly accept any JS code as TypeScript, and simply turn it as the same JS code, with the correct compiler options). 

In such a JS-TS code, most bindings have to be *implicitly typed* as `any` to fit this scenario.
There's no reason to do that for code which is originally written in TypeScript.

When you have to use, for example, `getUserInput()` function which is already implemented in Javascript, a declaration with `any` return type sometimes can be used as a shortcut when actual return type is not obvious, and you don't want to spend time beforehand figuring out which type exactly is returned in which circumstances.