* Building code is constantly updated, and this makes old built homes undesirable - building itself is worth 0 yen after around 7 years;
* Shrinking population means most real estate is actually empty/abandoned on low demand areas;
* Very disaster prone area so most buildings are either new (and build code compliant) or constantly being tested for disaster resistence;
* Few invest on real estate speculation as the return-on-investment is horrible.
I'm no expert, but when I was in Turkey in 2010 I took pictures of soft clay hollow bricks that were being used in new construction for the bulk of the building. You've likely seen pictures of similar bricks as they are used all over the world, but they are as fragile as eggshells.
They built the buildings without adhering to code. They get a project approved, do whatever they want (steal materials, build another floor, decide not to dig a foundation) and sell the projects advertising that the buildings are upto code. As we have a highly corrupt government, they pay their bribes and get the building approved. Also, the building inspectors are private companies, they approve buildings without ever going on site.
Even newly built government buildings such as hospitals, airports collapsed!! Even those buildings were built with bribes :(.
Corruption killed us here :(.
That said: there are always "grandfathered" buildings which were built before the latest codes; unreinforced masonry, for example. What politician wants to tell the owner, "hey, sorry, you've got to tear that down" ?
So, aside from builders ignoring codes, I wonder how many of the buildings in Turkey were built before earthquake-proofing was required?