How do you know which engineer(s) are responsible? Maybe Alice and Bob both worked on the product but Bob spent all day on HN and Alice did all the work. And what about Charlie who joined after feature completion but fixed a couple of major bugs and closed a security hole that would have bankrupted the company had it been left open?
It's just unwieldy compared to the salespeople case.
It's just as complex with salespeople. What about Alice and Bob visiting the customer together for two presentations and then Bob closes the deal on the third presentation he does alone. What if Alice lives in Kansas and meets Charlie the Customer in Europe on vacation, should the European sales guy Marco get a piece of the action?
It's just unwieldy compared to the salespeople case.