Why do crypto apps ask for SSN?

Can you explain why cryptocurrency apps often request for a Social Security Number (SSN) from their users? Is it a standard practice in the industry, or are there specific reasons behind this request? Does sharing my SSN with a crypto app pose any risks to my personal information and financial security? How can I ensure that my SSN is being used securely and only for the purposes it's intended for? Lastly, are there any alternatives to providing my SSN when using crypto apps?