This can eliminate the need to carry all those keys with you and limits the areas to which other persons have access.
Whether you need to control a domestic building such as your home, or a large scale commercial or industrial complex, having total control of access to all entry points through a Master Key system makes a lot of sense.
A Restricted Key System has the same potential as the Master Key System with the added advantage of complete control over the entire lock and key system i.e. no work can be legally performed on your system unless you authorise it.
Also, the only locksmith that can work on your system is the locksmith with whom the system is held.