A lot of the time, the user wont need to enter additional information about their order especially if shipping is disabled. Typically these notes fields will let the store admin know when is a good time for delivery. But remember, the less options the user has to complete, the more likely they are to become a paying customer. Sure, you could hide fields using CSS but this doesn’t actually remove them, it just hides them from the user. Unsetting fields using PHP is a lot more practical in the long run. Removing this optional field may be beneficial in some contexts, and here’s how to remove the heading, label, and field itself.
/**
* Snippet Name: Remove the Order Notes field section from the WooCommerce checkout.
* Snippet Author: ecommercehints.com
*/
add_filter( 'woocommerce_enable_order_notes_field', '__return_false', 9999 );
add_filter( 'woocommerce_checkout_fields' , 'remove_order_notes' );
function remove_order_notes( $fields ) {
unset($fields['order']['order_comments']);
return $fields;
}