Similarly, providing a fast shipping option is critical to ensure a market majority is addressed. Without fast shipping, a certain percentage of customers will shop elsewhere.
And, similar to free shipping, up until this point fast shipping was usually passed through to the customer. Want that jacket tomorrow? Pay $25 for FedEx Next Day Air.
Now that you have two carriers and multiple methods in place, it is increasingly probable that you can find fast shipping via a cheaper method that will probabilistically deliver on the date promised. For example, maybe the FC and the customer are located in the same state, in which case you could offer next-day shipping for free, then simply pick the cheaper UPS 5-Day Ground method during fulfillment knowing it will, in fact, get there tomorrow.