What is the purpose of the rear pockets on bicycling jerseys?

[Hot Steppa]

I noticed that most jerseys have three pockets in the lower back area. is there a specific purpose?

 

[Skyhawk]

They hold food. (like bananas, energy bars, etc.)

 

[skierboy]

Yes, it is for holding waterbottles

 

[La Bong]

They are for holding Roids and HGH.