Why do Nike dunks crease so easily?

That's because when you wear them, you move in them. The natural movement of your foot bends your shoe, causing it to crease over time. If your shoe didn't move with your foot, you'd be pretty uncomfortable. The movement causes the material in the shoe to compress, which can cause an unsightly crease or wrinkle.
Why do Nike dunks crease so easily?

The Crease Beast Duo

Nike Dunks crease easily due to the natural movement of your foot while wearing them. As you walk or engage in any physical activity, the shoe bends, resulting in creases over time. This flexibility is necessary for comfort, but it also causes the material to compress and develop creases or wrinkles.