Shipping costs are very low on many products. QVC negotiates a much lower rate for shipping and insurance than I could ever pay independently.
If I waited only until free shipping days I would miss out on some great items!
Tonight I purchased the Givenchy lipsticks, which provided free shipping for everyone. The lipsticks all sold out in fifteen minutes!
I also buy from the Lunchtime Specials and Primetime Specials as soon as I see something I really want, because items are limited and prices change.