Late Requirements

In software engineering, there always seems to be a trend about late requirements.  My wife is doing consulting work for a company that keeps adding requirements, but wont push back the deadline.  During my most recent company project, I was getting new requirements after the code lockdown date.  Then, management started complaining about the large number of defects created after code lockdown.  In the Agile world, late requirements aren't supposed to be a big deal.  When a requirement is added, another is supposed to be delayed, though.  I don't see this happening often.

The problem isn't in the development.  It isn't an "IT" problem.  It is a client problem.  Clients are the ones demanding these requirements.  They are the clients and they are the ones signing the pay checks, but clients need to understand that time is finite.  Software engineers can't stop time to work on requirements.  As a profession, we need to put our feet down and put the ownership of the problem back on the clients.  If they want to add late requirements, then they need to agree to extend deadlines.