You pay extra but for what??
A letter sent 1st class gets delivered 1st time whilst a recorded delivery letter can't be delivered without a signature so may not be delivered at all if you are not in or may be delivered to someone in your road with a signature.
So 1st class gets delivered 1st time whilst Recordeds might end up with a neighbour or returned to the delivery office.
Also how does the customer(the person who sent the item
Also there is no way of Customer Services the DOM or the Delivery Office to check where the parcel has been delivered to without asking the postman.