You need to take your shoes off
in the Japanese house because:
1. It is a sign of respect and a Japanese custom.
2. The outside is dirty, and the inside is clean.
3. The floors may get: damaged, darkened, dented, dirty, discolored, disentegarated, depressed, dusty.
3. All of these things would be disasterous.
4. The floor would be doomed to destruction.