1) Pilotless Planes would be more expensive to operate than hiring a couple of pilots.
2) Someone still has to sit and control these aircraft
3) No current or planned airliner is capable of being converted to pilotless operations without punatitive conversion and certification costs.
4) Its a terrorists wet dream.
5) A large EMP event would render all airborne airliners uncontrollable (range 350nm radius of - say - Paris) and such capability will be in non-state hands within 20 years.
Cheers
WWW