I know it's not correct that's why I raised the question. This was not a question of "DO-IT-YOURSELF" mentality. In this case the aircraft was no 2 for landing, the controller tried several times to give the clearance after the runway was vacated, the aircraft transmitted back they could not hear them.
How can you "assure yourself there is no traffic on the runway"
You can also change the question to how does the controller know for sure there is nothing on the runway. Of course you can't be 100% but every landing I try to assure myself there is "no dead whale on the runway", even if I have been cleared to land. team work.