I'm surprised to hear you suggest there aren't many. Maybe the question needs clarification, I'm not sure.

I'm surprised because we regularly see buildings over a century old. You have buildings like Yin Yu Tang 蔭餘堂 (which admittedly was relocated to the US), the entire town of Hongcun 宏村 in Anhui 安徽 province.

In Taiwan it's not at all uncommon to see older Japanese-era wooden homes, though in my city at least most were destroyed when the American bombers flattened much of the city in the 1940s.

Places like China and Japan and Korea have a massive number of old buildings. I could list a bunch more but it would take all day.

Now, that said, materials do play a role, but people play a bigger role. In 2008 the city gate in Seoul called Namdaemun ("main south gate") was set on fire, destroying the wood section. The Taiping Civil War did a lot of damage to buildings, as did the Second Sino-Japanese War. The various reforms in Communist China as well as later economic reforms also had an effect.

So while yes there are reasons we've lost a lot of old buildings in East Asia, we're certainly not lacking them today.

edit: I didn't even notice this part initially, but "Oriental" isn't really a good word to be using here. It's pretty loaded and some people will take offence to it. Can't be helped now since you can't change titles, but maybe something to avoid in the future.