It is rare for a client to insist on unlimited use of the images they have commissioned, as this can be a costly affair. The price of the job includes the agreed media – an unrestricted licence would include every possible media including billboards, videos, TV, CD’s, t-shirts etc - worldwide for the term of copyright, which is 70 years after the photographer dies. If professional models are needed for the shoot their charges also reflect the use to which the image is to be used. The price for this type of licence would be enormous and you would be paying for use you do not need. This is like buying a car to make one journey when you could have hired a car at a fraction of the cost.
To be fair to the client and ensure they get the rights they need, a system has been agreed with commissioners for negotiating licences.

Click to see AOP guidelines for negotiating licences in Adobe Acrobat PDF format.