Higher ping times, or higher latency, are the result of the network traffic having to queue up similar to waiting at an on ramp to the freeway. If the freeway is completely full of vehicles you have to wait to enter into traffic.
There are several factors that increase the round trip ping time, or latency. Many devices in the home that are consuming the entirety of your available bandwidth, noisy Wi-Fi environment (a lot of wireless devices), high usage of the streaming or gaming server you are using, and extremely high usage of the network as a whole can increase the wait time and latency.