Here’s what consumers have asked with answers from WSJ Wine staff and previous consumers.
Because their service sucks and very quick to deduct the card but very very sloppy service
They also have a "free shipping" program called Advantage Shipping Service that you can buy (a la Amazon Prime) for $89/year. I've never purchased it because it's only valid on full cases, and I don't usually buy enough of those in a year's time to justify the $89. But if you buy at least 5 cases a year, regular shipping costs you $100, so the Advantage program is worth it in that case.