Deadheading is one of those tasks that seems silly, but it is very important for the flowering strength of your plants.
Removing the old flowers keeps you plants producing more flowers. Leaving the old flowers sends a signal to the plant to stop flowering and wind down for the season. Take a few moments each day and snip off the old spent flowers so you will have continual blooms throughout the growing season. You will be amazed at how happy your plants will be!