I have LG Washer connected to my network. The network stack on my model is terrible and would constantly fail after period of time receiving multicast packets from other devices. I had to segment it on to it's own SSID/VLAN/IP Address and ensure no other traffic reached it. It has been stable since then.

Mine has only used 3MB over the last month, which seems low.

As to why. It is connected to home automation system and will announce on Sonos when the wash (or dry) is complete. I also had it connected to LEDs on light switch that would blink when clothes were in the machines waiting to get moved.