Why is Public Interest Registry limiting WHOIS Port 43 access for the general public?

Why is Public Interest Registry limiting WHOIS Port 43 access for the general public?

Public Interest Registry is committed to protecting the rights and privacy of registrants of our domain names. The previously unlimited access to Port 43 led to abuses by speculators and data miners, often using automated programs to make inquiries. Rate-limiting logic was introduced to reduce this.