What is the point of forwarding calls to collection in paginator instance?

[mikeydevelops]

So, AbstractPaginator forwards its calls to the underlying collection instance and returns the result of the collection methods. As we know, most of the collection methods are immutable, i.e return new instance instead of modifying the current one.

Example

Model::paginate(10)->shuffle(); // shuffle gets proxied to the collection and paginator is lost.

// If you wanted to do the same but keep the paginator you have to assign it to a variable.
$paginator = Model::paginate(10);

$paginator->setCollection($paginator->shuffle());
$paginator->setCollection($paginator->getCollection()->shuffle()); // same as the above but more explicit and understandable.

My question is why are the paginators forwarding calls to the collection instance?