Many AMers don't think that's important, and you hear QSO roundtables with stations 1, 2 and sometimes more kc/s off frequency from each other. Not only does that make the QSO take up unnecessary band space, those receiving with a synchronous detector sometimes have to switch to envelope mode because it may take a second or more for the BFO to re-synchronise with the off-frequency carrier; an off-frequency breaker may not even be heard because his brief transmission is over before the detector has locked in. With a fast-break QSO, receiving with a synchronous detector is usually impossible because inevitably stations in the group won't all be on the same frequency. Those using modern day transceivers with digital display shouldn't have any problem zero'ing. All they have to do is adjust the transmit frequency to line up with the VFO in receive mode.