It just feels good.
Some people need to be convinced. Do my icons really need a texture? Do my keyboard keys really need a shape? I can see what I'm doing, why do I need to feel it? These are the functionalists, the people who would strip the world of it's "unnecessary" parts. Why buy art when the wall is already painted? Why see live music when it's free online? Why light a candle when fluorescent lighting can flood the room?
Tactile displays aren't for functionalists. They are for living, feeling human beings. It's a sensory experience. Instead of feeling that sticky, greasy feeling, you feel the richness of materials, the contours of objects, and the crisp feedback of your actions. Everything you've ever touched has a texture, except for the icons on your smartphone screen. We're bringing the richness of the real world back to your fingertips, and it just feels good.