Quite often just means the ATC doesn't have the required runway separation standard eg busy day, trying to squeeze out as many departures as possible and someone rolls a little slower than expected meaning they haven't rotated by the time the arrival will cross the threshold.
If something like this happens in South Africa, the ATC is suspended immediately (guilty) because somehow/someway he made a mistake and must be punished!!! Poor suckers!!
This morning had Air France landing with wet slippery runway(with high speed exits), bit of a cross wind but he slowed enough to exit the next taxiway 400m ahead(30yrs of judgement) and came to a basic halt on the runwat before turning off. When told to expidite,(other traffic 2nms behind, 4 at the holding point and 3 more 7nm appart on final) he started mouning ..very heavy....and that he should have vacated at the end(4000m runway). I think this is and excelent example of professionalism?? Landing clearance given eventually 1nm final!!
Sometimes ATC's must have hair on their teeth to handle these situations...trying to accommodate everyone with minimum delay.
Just wanted to moun a little. SRY
RE