And also because it would be useless.
Most sellers and most items on eBay are offered at Fixed Price. The seller does not see anything about the buyer until he has bought.
Instead, seller with Unpaid Items file a Dispute with eBay against the bidder. If the bidder does not pay, the seller gets her fees back and the bidder gets a Strike on his buyer account.
Sellers can set a Block against bidders with Strikes. This is automatic. I just checked and three potential bidders were rejected in the past 90 days on this account. I had no idea. Less work for me.
The seller also gets her FV fees back. Bonus.
Go to your Seller Preferences and set up Blocks against bidders with Unpaid Item Strikes. While you are at it add a Block against bidders without an active Paypal account. If you were selling at Fixed Price you could also demand Immediate Payment, but this is not available for auction listings.
You can also Block bidding from unwanted countries. Like Nigeria or Malaysia.