I own a few domain names and they ask me to update this info one per year. I've never understood why they need it at all though. Why should they have my address/contact info and why should it be publicly available? I'm sure the answer is obvious but I can't figure it out.
Regarding Why - ICANN runs on a multi stakeholder model, meaning governments and legal entities get a seat at the table too.
They have an interest in knowing who is behind a domain - its that simple.
Also whois privacy is not the protection everyone thinks it is. Its a lock on a door. It keeps casual looks out - spammers, scammers, etc.
If a government or police organization wants that information and they have legitimate need to do so, they will get it.