Catering...Why?!?!?

I have a question... I`ve come across too many reception halls that say that the only way you can serve food at their halls is if you have a licensed caterer do it... WHY?!? Is there a way of getting out of that? All the parties/weddings I`ve been to my entire life have had the food prepared by close family and friends...can`t I do this for my wedding too??? Any suggestions?? PLEASE HELP ME!!! (my email is bubblesbxny@yahoo.com)