As well known, human beings are bad at predicting the future. Having worked on different kinds of projects, I can say that engineers who are supposed to do the project work are reluctant to schedules. Their attitude is rather skeptical. Why trying to predict if the schedule will slip regardless?
However, as Scott Berkun has put it in his book on Project Management "Making Things Happen", all schedules serve three purposes:
"The first is to make commitments about when things will be done. The schedule provides a contract between every person involved, confirming what each person is going to deliver over a particular period of time.
"The second purpose of a schedule is to encourage everyone to see her efforts as part of a whole, and to invest in making her pieces work with the others. Schedules force everyone to carefully think through the work they need to do.
"The third purpose of schedules is to provide a tool to track progress and break work into manageable chunks."
That's why the project schedules are still important to create and maintain.