WHOIS is a relic of an older, friendlier internet
WHOIS contact details are a relic of the 1990s, when everyone ran fingerd and identd and sysadmins could solve problems by calling each other up for a friendly chat.
Nowadays putting that kind of personal information publicly on the Internet is just asking to be scammed and abused. Last time I published my real phone number in a WHOIS record, I got about a dozen telemarketing and scammer calls a day for weeks. My phone is still largely unusable for incoming calls (because I just ignore it.) At this point it's just a way for registrars to make more money by selling "domain privacy" packages.