I like to pick my own groceries... How do you know if you order online they won't give you a bruised apple, or not as good of date on your milk etc....
Plus I compare the different sizes and prices and change my mind all the time, so I couldn't do that with pick up orders...
Sometimes two smaller ones are a better bargain per ounce than the larger packages, we are programmed to automatically think buying the larger one is getting it in bulk and a better price per unit... Ie: sometimes they put the 1/2 gallons of chocolate milk on sale for $1.99 and regular price on the gallon is $3.99, so you can get two half gallons for $3.98 - yeah it's only a penny, but I've seen bigger price differences on other items... It's cheaper to get three 500 packs of Q-tips than two 750 packs....