Sanitization with form validation

Why we cant use trim(), htmlspecialchars() like methods in form validation rules?

for example......

PHP Code:

'name' => [
    'label' => 'Name',
    'rules' => 'trim|htmlspecialchars|required'
]; 


Is there any easy way that we can sanitize $_POST data at once? 

I know we can do something like htmlspecialchars($request->getPost('name')); 

But its nice if there any way that can pass a array like validation rules and sanitize multiple post vars at once. than wrapping with php native methods.

thanks.