If you run your LAN party properly, then your guests are the primary reason for which you run your LAN party, and they are the reason you can run your LAN party. Secondly, your network should be one of the reasons they attend your party. Without a good network, your guests may not have as good of a time. If they cannot use a network with lower latency and more bandwidth than their home Internet connection allows, then that is one less reason for them to not attend your party.