Here's a good reason to include an up-to-date address for every entry in Contacts: You can then use Maps to quickly get directions to the location of any person or business in Contacts (And set location reminders!)
To get directions to the location of one of your contacts, open Maps and tap on the bookmark icon in the top right corner.
This will open a list of all your contacts. Contacts with an address will be highlighted.
Tap on the name of the contact whose address you want directions to, and Maps will quickly show you the location without you having to type anything!