Let’s face us, traditional means whatever we choose to let it mean. From the time karate transplanted into Japan, many things started changing.
If we try and understand what karate was prior to 1900, there is little available documentation.
The training was more private. There were not formal training halls, often classes were held outside the instructors home, and perhaps inside.
There were no special uniform for training. The reports we have seem to indicate that students just removed their garments and trained in what was almost their underwear.
Now we all know training can be hot and sweaty business. I am sure if they were wearing their street clothes, they did not want to sweat in them. Still Okinawa has a winter, and then I imagine something heaver was worn.
The idea may have been tactical. As there was Sumo on Okinawa, removing ones clothes would have meant the opponent did not have your clothes to use for grappling.
In any case they were giants in those days.