I would like to know: what were the houses in Sichuan built with in the past? Why is there no steel reinforcement?

Houses used to be wooden structures. At that time, being able to live in a big tile house was equivalent to people living in villas today.

Steel was a luxury for people at that time; the Chinese used to call iron nails "yangding", so there was no steel.

Later, people began to build brick and wood houses, basically one or two stories high, also without rebar.

Nowadays, you don't use rebar in a house, do you?