While broadcast address in IPv4 is used to send traffic to all the hosts in the network, then what is the purpose of network address in IPv4 network?
IPv4 address are used to locate a network host (PC, Laptop, Ip Phone, cell Phone and a large etcetera...). Each host must have a IPv4 Address when you need a type of traffic called unicast, wich means a communication between two network hosts, like visiting a web page, senf a file or send an email.
If each communication send a broadcast to every network host, each host can view the web page, the file or the email (this is not exactly technically, but illustrate my point)
and last, to make an example, if each communication are a broadcast, is like every phone call is share by every phone, or every letter is send to everyone.