Credit card integration obviously generates more tipping, otherwise we wouldn't be talking about it.

This is because once they see the prompt, many people think of the tip as mandatory (vs may not have thought about it) - or they don't have cash but now can tip. A good thing. I always tip well.

Now coffee becomes a thing you tip for, for these people. Totally voluntary.

For those people, this raises the effective price of a cup of coffee.

Getting Starbucks now becomes a costlier habit. At the margins this can drive someone to go elsewhere, skip, etc (basic supply and demand.)

This may not apply to some given individual but across millions of customers over a long time price including tip obviously affects quantity demanded.