Why sunflowers face east?

To get the most sunlight. If the sunflower isn't turned towards the sun, the sunlight is hitting its' side, which isn't as wide as its' front. It also closes when it's dark and opens when it's light. By the way, lots of flowers turn towards the sun in the first place for photosynthesis, for the nutrients.
YOURMOM

Sunflowers turn toward the sun because they need sunlight to do photosynthesis. Their leaves hold Chlorophyll which turn sunlight into the energy they need to survive.