Another reason we use such phraseology is so that we 'own' the r/t at critical moments.
By adding the 'landing traffic...' part to the take off clearance, we can spool out the moment and launch the departure at just the right time, reducing the ability of someone else transmitting at a critical point.
Last year, a B752 departed on a SAM, inbound checked in at 7nm. BA146 on a SAM given line up & wait as it's a 2 minute departure separation.
Just as the ATCO was about to launch the BA146, the inbound started discussing ILS fluctuations and didn't stop talking until he was at 2nm.
The ATCO replied that no fluctuations had been reported and that he should go around I say again go around acknowledge.
A very surprised missed approach was carried out
