Have ever had that unpleasant feeling of having to make a present to someone, but not knowing what to buy? 99% of the times, this type of uncertainty does not help users completing their purchase.
The same happens on your shop. A customer comes to purchase a present, browses the catalogue in search for an idea, but he cannot be sure about what the recipient could like most and has many doubts: how does refund policy work in case the product should not be good? And if the size were not the right one? And if it did not arrive in time?