That's not why Starbucks is so labor-intensive.
Starbucks developed a good automated coffee-making machine, but decided not to deploy it. Instead, they built a lower-profile manual machine which allows their employees to maintain eye contact with the customer. The whole point of Starbucks, the thing that justifies their high prices, is the ego boost the customer gets from making the barista perform. Starbucks is about sucking up. All their employees know this; it's in their training. Starbucks is a fast food operation with the sucking-up level of a sit-down restaurant.
Read what their CEO has to say on the subject.[1]
[1] http://www.kplu.org/post/robot-baristas-heres-starbucks-ceo-...