So many reasons! Brows lighten from the sun so the ends are lighter than the inner edges meaning that when you tint them, the full hair has color and definition Years of over-tweezing leads to sparse brows, if you add color to them, they naturally will look fuller and cover up patchy areas Finer hairs will be more pronounced when tinted giving you a fuller looking brow. This is especially true for the very fine and non pigmented hairs at the start and end of your brows Use less make up and save time in the morning !