For safety, it is not advisable to make use of personal email or phone number in some websites, though, most websites requires it. Most times, for confirmation that it is human who owns the account created, and not just a bot or random account creation. Another thing is when the site requires KYC, and any site that requires KYC is a site that needs identity of its users based on government intervention/agreement between them, probably for monitoring activities of money laundry/fraud.
On daily basis, our identities on the surface of the internet becomes more visible, cause as new technologies are coming into the market, tracking and tracing of people or identities are become more simple and easier. It is good as a crypto user, not having anything to do with fraud and money laundry, so as to avoid ill act coming against such person.