Ok, this reason may not apply to our store initially but it definitely is another reason I look forward to the Costco opening...because it might happen.
You may ask, "why do I need 1.75 liters of liquor at a time?" Let alone the opportunity to purchase multiple bottles of this size. To put this in perspective, a fifth of liquor is 750 ml, these larger bottles are more than twice the size of a regular fifth. So back to the original question. It's not a matter of needing a "handle" of liquor. It's a matter of economy. Liquor will last a very long time even when open. Typically the prices seen at Costco justify the extra volume. And, in the end it's pretty tasty stuff.