The purpose of the secondary bidder field (most commonly the spouse field) is to allow two active bidders to be linked on the same account with the same credit card.
The secondary bidder has a required phone number field. This allows both phone numbers to be able to login to the account, place bids on items (we make it clear who's winning so no one is bidding against their spouse), and both receive outbid messages and texts blasts before and during the event.
Remember this very important distinction, accounts and tickets are two different things. Some accounts have a ton of tickets while other might not have any tickets. The check-in screen operates on tickets, so creating a secondary bidder isn't claiming the second ticket for this person. You also need to scroll below to edit the ticket information for the account.