I don't know how widespread the sterile cockpit rule is over the entire aviation community, it's obviously quite common amongst airlines. In the UK military there's no such rule! The crew can speak whenever they want, silence tends to fall on the take-off roll and short finals but other than that it's chit chatty. People learn to listen out for the callsign on the radio, and when the tone of voice changes to run checklists or perform a mission-based task everyone goes quiet before resuming conversation post-event. No need for such 'draconian' rules!