Why the Number Isn't Fixed
A veneer's job is to change how a specific tooth looks, so the number needed is really a question of how many teeth need changing, not a standard package. Someone with one discolored or chipped front tooth might only need a single veneer, or two if matching it evenly requires treating the tooth next to it as well, since shade matching a lone new veneer against older teeth can be trickier than it sounds. Someone unhappy with the overall shape, color, or evenness of their whole smile is a different case entirely. Both are legitimate starting points, and neither one is automatically the correct amount of treatment — the goal is matching the plan to what's actually bothering you. Talking through specific goals before counting teeth is usually a far more productive way to plan a case than starting with a target number and working backward from it.