Why does neither Sam’s or Costco have a gas station in South Austin locations???

I have been wondering for a while why is it that both Sam’s and Costco South don’t have a gas station while pretty much every other location has it. Is there any particular reason?

First I thought space but seems too convenient that both locations don’t have it.

Any thoughts???

Clarification— Referring to Sam’s off 290 (Southwest Parkway) next to Specs