To thunder 78
I thought like you until a very wise old project manager pointed me in the direction of business risk. It goes like this:
Business "we want the project yesterday."
IT Project Manager "We can give it to you yesterday but it will be made out of string and duct tape and these are the business risks:
Business process A will fail as the expected uptime is only 65%.
Service and Maintenance costs will increase on the system by 4000% over its life.
It will compromise the security of our mission critical systems.
But if you'd like to sign off accepting responsibility for those business risks we'll deliver tomorrow."
I haven't found a business sponsor who would yet!!!