There's a whole lot that is more exciting than watching grass grow. Two examples would be watching milk curdle or paint peel. Grass grows very, very slowly - approximately 3-5 inches per week depending on temperature, fertility, moisture conditions, and season. That's about seven hundredths of an inch a day, three thousandths of an inch an hour, five millionths of an inch per minute or eight trillionths of an inch per second. This is not enough movement for the human eye to register. Pretty boring.