On a continually changing network it is often difficult to spot issues due to the amount of noise generated by expected network traffic. Even when communications are seemingly quiet a packet sniffer will display screeds of noisy data.
That data might be otherwise unseen broadcast traffic being sent to all hosts willing to listen and respond on a local network. Make no mistake, noise on a network link can cause all sorts of headaches because it can be impossible to identify trends quickly, especially if a host or the network itself is under attack. Packet sniffers will clearly display more traffic for the busiest connections which ultimately obscures the activities of less busy hosts. .