Why Probiotics are combined with Prebiotics?

Look into the above prebiotics and probiotics formulation as for understanding purpose. 

Probiotics are the beneficial bacteria in your gastrointestinal system that work with the body to maintain a delicate balance between the good bacteria and bad bacteria, a process that is essential for health and well-being.
Prebiotics act as nourishment to probiotics and are non-digestible foods that make their way through your digestive system and help good bacteria grow and flourish.