Why blade technology was developed

Only the first 30 seconds of the video are important:
https://youtu.be/cL3nWqvzfow?si=fz6wc48MFo36Bbbg
Literally there are *no* other purposes for blade technology, even today. On the other hand, this particular job *demands* blades, because you cannot cut one by one stem, the only senseful thing to do is to cut them in a sheaf. And blade technology is ancient, I believe that they have evidence 700ky - 800ky old.