The one time offer (OTO) is a big feature for any affiliate manager, but making the customer go through the checkout process again and again is not only a pain for your customer, it ultimately means less money for vendors. This is bad for everyone.
PayGear vendors get the benefit of adding one click upsells to their sales funnel. The customer just clicks the buy button a single time to add the additional products to their purchase. No need for the customer to reenter their name and credit card or go through the PayPal checkout a second time. That is pointless, the info is all going to be the same anyway.
At PayGear we make things easier on our customers by giving them real selling tools they can use in real situations.