[TheCoelacanth]

Of course, that is not what anyone is claiming.

With sales, it is very easy to tell which specific people are responsible for any specific deal. That's why sales compensation usually includes a share of revenue.

With product development, unless you have a very small team working on the product, it's nearly impossible to tell which specific people were responsible for a specific chunk of revenue. When someone buys a product, it's hard to determine which specific features were responsible for the deal.