The trouble with a drinks machine where clients can help themselves is that some clients take advantage and end up drinking about 3 cups of coffee etc. I'm all for hospitality but that's taking the pee.
I know from experience as a salon I used to work in had one and there were a few clients who used to drink about 3-4 cups. Same with the water machine they had. If we were busy there would be those plastic white cups and spillage from what wasn't drunk all over the place. Pain in the butt.
I would rather have the option of offering a drink to a client rather than them helping themselves.
I don't own a café I own a beauty salon.