A shopper just missed the shipping cutoff for Christmas delivery. They ordered online anyway, or they’re standing in front of your site right now trying to decide whether to bother. The only thing that gets them a gift by Christmas at this point is picking it up in person, buy online, pick up in store. If that option actually works, you’ve got a sale and a loyal customer. If it doesn’t, because the item your site said was available isn’t actually there, you’ve got an empty-handed shopper on the one day they had no backup plan left. That’s not a hypothetical.
