Biden/Harris probably realized they would have been unwelcome and likely heckled if they went. Similar to the Kathy Hochul story where she tried to attend a fallen officer's service.

All the idiot "journalist" had to do was some basic research. Only 4 participants are allowed at a requested ceremony. The family obviously didn't want a commie there:

Public Wreath Ceremonies

A group may honor U.S. veterans and members of the armed forces by laying a wreath at the Tomb of the Unknown Soldier. Public wreath ceremonies are limited to one per group per day, with a maximum of four participants in the ceremony. The wreath for the ceremony is provided by the participants.

From: https://www.arlingtoncemetery.mil/Visit/Events-and-Ceremonies/Request-a-Ceremony