Buying anything, no matter how big or small is not a worry from any shop I have ever known or worked in. Asking for free product or even demanding anything including a discount is a good way to get you a reputation for being a dick.
I have always believed in the "free plain grip with every deck purchased" and almost all the good shops do it that way, but a lot of shops have decks and grip sold separately or have run out of stock, so sometimes a guy does have a board from one place and grip from another.
It is funny to see kids with special edition or team rider decks hustled at the local park coming in needing grip, or if a big comp has been on and half a dozen people all come in for grip because they won a deck that weekend.
Every time someone asked to regrip a deck where ever I have worked, the first thing I do is check the grip that is currently on there, politely ask why they wanted it regripped (and explain the process, especially if there was nothing wrong with it) and then also politely say they need to remove the grip themselves first.
Sometimes it comes up in one nice even sheet, but other times it comes away in thumbnail size pieces and could take hours to get off.
Most of the time, it was kids wanting a fancy printed grip sheet instead of the normal plain black their stock complete came with, and almost all the time I said to the parents there was nothing wrong with the existing grip and to put the nice fancy grip on the next deck they buy, to which they agreed, so it was a win win.
Sometimes they would even buy the new deck right there and then as well, which was even better.
Gripping decks is not only a skill, it is an art. If you don't know how to grip a deck, you should at least pay attention or try to learn, but I am always happy to grip a board or set up a complete from anywhere and for anyone. At least I know it is being done right.
Skateshop 101 : NEVER ever run out of griptape, but I have seen it happen way too often in almost 40 years skating.