Why are centerfield seats purposely empty in baseball stadiums?

Answer 1

If the stadium is strictly a Baseball stadium, there won't be any seats in center field, and if it's a multipurpose stadium they will be covered, and unused.

This is done for the batters... That area is what is known as the "batters eye" which means it's the direct view of what the batter sees from home plate. It's generally a dark color (so the ball can be easily picked up from the pitchers hand), and if there is a video board, it is on a fixed picture during an at bat.