Surely if ATC request a speed in regulated airspeed and the readback is correct but then the aircraft does not comply then an offence is being commited?
These pilots and airlines that do not comply should be prosecuted as to fly in this manner may be to endanger the aircraft and its occupants not to mention other airspace users.
As a pilot who is (semi) retired from the industry I dearly loved I am quite appalled to hear of such antics from so-called professional pilots!