It's also the problem that software is not strictly a product, but a mix of service and product. There's the core product that you are selling (say e-commerce)

It's also the problem that software is not strictly a product, but a mix of service and product. There's the core product that you are selling (say e-commerce) and there's the customization service that's been sold to increment the product per-customer basis. Traditional sales knows how to sell either a product or a service, hardly the mix of them, which makes software special (but not unique).