In csapp, what is the read_requesthdrs() function effect?

In csapp, there is a project called tiny web, in the source code, the sever reads request line from sockfd, then it calls read_requesthdrs() to remove request headers from socket receive buffer. The book explains the server doesn't need these header information.

My question:
Why does the server need to remove these headers?
I comment this function, that mean the headers still in the receive buffer, but the browser can still get the resource files from server. Does anyone know the reason?