Meditation can help put you in a deeper state of relaxation, which can in fact lead to feeling sleepy and tired.
Many people actually take advantage of this to help with their sleeping disorders. They may choose to meditate right before bed, or they may even choose to meditate while laying down.
For some, meditating is a way of ending the day, before going to bed. It allows them to clear their minds from the day that has ended, and go to sleep with a clear mind, free of unwanted thoughts that may keep them awake, and free of unwanted feelings that may prevent them from getting quality sleep.