Yes, you should make them.
Most piercing studios operate on a first come first serve walk-in basis. The only reservations will be in the context of a second appointment after consultation (for example to decide on placement or jewelry for something unusual).
Tattoo studios on the other hand almost always recommend that you call ahead to make an appointment (and often go in person to leave a deposit).
A quality artist needs time to work on your design, even if it's one you brought in. In addition, due to their talent being recognized by the public, a good artist is booked at a minimum weeks, often months, and sometimes even years in advance.