From a business point of view, I do not really understand why to spend time and effort on this if the transaction costs are covered by clients in one way or another. But such a decision would be very clever from a marketing point of view, since by spending a little money on updating and implementing this feature, you subconsciously convey to customers the idea that transaction costs on your platform are lower than on competitors' platforms,
This is exactly the reason I use instant exchangers instead of "normal" exchanges. Withdrawal fees are 0.001 BTC on many sites (and 0.0005 on some). That's a lot if you're withdrawing only a small amount, but unfortunately the large exchanges don't seem to want to compete on this.