This is good advice for kids, someone who wants a toy, the occasional "player" in martial arts acting on their own or under an incompetent sensei.
I learned iaido in a dojo where only live blades were used. The headmaster was one of the top iai practitioners in the USA, Sensei Yamazaki. (Interesting note: He was Arnold's sword coach for the original Conan movies.) He was very old school, and the
dojo atmosphere was steeped in self-discipline and respect. These qualities are a must when slinging sharp steel around with a group of people. In the three years I studied there, no injuries occurred. (I did hear of one that happened a couple of years before I started - one of the black belts impaled himself doing a reverse thrust - he fully recovered. The story helped my own
gyaku tsuki become very precise.
) There is a definite mindset, a calmness, one needs. This attitude is maintained even when cleaning the blade after class is over.
.https://youtu.be/q_BZj4Sg45o
Using real weapons forces one to respect the blade and be mindful of
every movement. When practicing with "fake" weapons there is little or no danger in being sloppy. This can lead to bad habits and poses a danger in future use of a real weapon. The inherent danger using a live blade sharpens one's skills, physical and mental.
Such a discipline is not for everybody