a question about china............?

Because it would be rude not walk through the screen!

No. in olden times it is said that ghosts/bad spirits would only walk in straight lines and could not walk around objects. It is also said that sometimes they follow people home.

A screen is placed behind the gate so then a spirit or ghost tries and enters the home to haunt it the screens blocks it as it cannot walk around it.

The odds are that down the ages a custom was also added to human visitors to ward off evil spirits that may have followed them.....

As for stepping over the large threshold, it is meant to be bad luck if you step on it.

because of the way the houses were built back then. The front door looks like a gate, heavy double-doors. The doors are "off" the floor to prevent flooding, etc. So, to go into the room, you have to step over the "threshold" on the floor. Then, most rooms in a traditional home will have a screen, that acts as a divider between the room and the door (the door will be open because it's too much work to open the "gates" every time you enter/exit the room).

because the screen is actually a wall, if you do not go around it, you have to go through it. some threshold is very high, if you do not step over it, you will stumble over it.

in respect to the resident. gate means main entrance, so people dont think u are a thief sneaking in. large threshold is to make sure u sorta bow towards them. walking around a screen means respecting their privacy, not drawing it up wide open and scare the hell out of them.

Nobody lives in a traditional chinese home in china now lol

I've never heard of that.
In Chinese customs, it must be either for good luck or it's a test, purification?