It Makes Parallel Work Difficult
Management usually expects us to be done with building the software they sponsor at a certain date. Actually, they even expect us to be done within a certain budget as well, but let's not complicate things here.
Aside from the fact that I have never seen "done" software in my career as a software developer, to be done by a certain date usually implies that we have to work in parallel.
Probably you know this famous conclusion from "The Mythical Man-Month," even if you haven't read the book:
"Adding manpower to a late software project makes it later" – The Mythical Man-Month: Essays on Software Engineering by Frederick P. Brooks, Jr., Addison-Wesley, 1995.
This also holds true, to a degree, to software projects that are not (yet) late. You cannot expect a large group of 50 developers to be 5 times as fast as a smaller team of 10 developers in every context. If they're working on a very large...