Bealine, is self check-in any less secure than asking passengers damn-fool questions like "Have the bags been with you at all times"
I should bloody well say so! The damn-fool questions to which you refer are a "DfT requirement" (although not everyone now asks them)!
However, if nothing else, we are able to spot if someone has been drinking heavily or if someone appears excessively nervous or anxious! Passengers who make last minute bookings and travel with only light luggage need special scrutiny (based on previous history of terrorism) - particularly if they travel First or Business Class (front of aeroplane).
Bit by bit, the whole safety and security of our airports is being dismantled - sacrificed to the god of commercial pressure!