Coops has put it well. Accepting PayPal on pick up items leaves the seller vulnerable to chargebacks months down the track.

To the original point in layman's terms -

A buyer should inpect item before clicking BIN. If they are happy and put a deposit or pay, then if someone clicks BIN before purchaser gets back to a computer, seller simply advises item is sold. The way it has always been done in other media.

If a buyer clicks BIN, then inspects and item is not as described, buyer cannot be expected to purchase and seller does cancellation, gets fees back and re-lists.

If the item is as described (leeway needed as is subjective), buyer has an obligation to purchase as this is stated on confirming - By clicking Commit to Buy, you are agreeing to and entering into a legally binding contract to purchase the item from the seller. However there are some newbies out there and cancelling is better than pushing the issue.

If you seriously want immediate payment, select it in your listing set up and no one can click confirmation before item is paid. I don't think you were aware of that option. But is messy if you need to refund due to item not as described or buyer does chargeback months later, gets cash and boat.

Good luck.