Simple answer Too many instances of identity fraud. Did you get a letter from the IRS requesting verification?
Do not reply to email solicitation for information-the real IRS does not use that method. https://www.irs.gov/individuals/understanding-your-5071c-letter
Disclaimer: Not a tax professional. Information gathered from internet links. Anything dated in June 2019 was posted in prior years and is before the 2019 limits and changes.