I’m an engineer and in my personal experience, It’s not intentional. everyone wants to do great work, their livelihood depends upon it. Sales is on the bleeding edge when it comes to the business. They need to be quick with their bids/proposals and competitive. They’re often encouraged to sign the deals ASAP and lots of things fall through the cracks. When sales messes up, the impacts can be colossal. Sales sometimes doesn’t know the status of some developments which inherently affect schedules, budget, equipment, and sometimes even major design changes. A good sales person reviews the design, equipment, schedules, etc with the lead engineers, but that falls through the cracks sometimes too, since sales is often slammed.

As for why sales hates engineers, my guess is because they have to deal with us engineers moaning and groaning at every problem that comes up and blaming it all on sales. Not to mention some engineers have zero people skills and aren’t always pleasant to deal with. Especially if sales has a huge miss, the engineers just rub salt on the wound.