It’s required because once you transfer the license to a USB key, it can only be transfered to another key, and never to a hard drive again. So you have to meet with the buyer physically, or include your computer in the sale. 
It’s required because once you transfer the license to a USB key, it can only be transfered to another key, and never to a hard drive again. So you have to meet with the buyer physically, or include your computer in the sale.