Frankly the valve is often quality. Quite often something ships on a date. That something is usually crap.
In order to get schedule to change, you'd have to convince salespeople to do something. They are generally the ones doing the convincing.
In order to get the features to change, you'd have to get a product manager to give up what they want to build "because of technical reasons". That doesn't happen often.
But if the product ships with the new features on the agreed upon date, the only people hurt are the developers and the customers. Most people in the business who pretend to care about the customer experience are perfectly happy to do this because it gives them a big club to wield over the engineering team in future iterations.
In order to get schedule to change, you'd have to convince salespeople to do something. They are generally the ones doing the convincing.
In order to get the features to change, you'd have to get a product manager to give up what they want to build "because of technical reasons". That doesn't happen often.
But if the product ships with the new features on the agreed upon date, the only people hurt are the developers and the customers. Most people in the business who pretend to care about the customer experience are perfectly happy to do this because it gives them a big club to wield over the engineering team in future iterations.