The legality of whether or not to ID yourself to LEO aside, consider this:

If you choose to leave your ID at home when you go out for a ride, and you get into a bad accident such that you are rendered unconscious, how is the first responders/medical staff supposed to be able to even begin contacting your family or S.O.? Even if you respond with just check the cell phone you probably carry for the ICE contact, assume worst case and that thing is inoperable and that info is lost/unaccessible.

Carrying an ID just makes life so much easier.