A reader offers this perspicacious take on Starbucks:

I suggest the title: "Starbucks is firmly in the tinkering stage".
  

All retailers see their sale growth shrink to single digits once they saturate the market geographically. They then enter the tinkering stage where they try things like this that usually have roughly net neutral trade-offs.

Focus on quality (or consistency) and you attract clients that value that and lose some that value convenience. Focus on convenience and you lose those looking for quality.

But, it never hurts to experiment. After all, nearly all successful products and business are the result of a successful experiment.