Why doesn't the appraisal value of a house go down as it gets older?

The appraisal value of the house is the construction cost required if the same house that was the subject of the appraisal was to be newly built on the same location at the time of revaluation, that is, the rebuilding cost, and the construction cost of the house. It is obtained by multiplying the depreciation point correction rate that expresses depreciation due to the state of wear and tear that normally occurs over the years (However, if the value exceeds the value of the previous year, it is usually left unchanged at the value of the previous year. ).
For some houses with old construction years, as construction costs continued to rise in the past, the appraisal value was left unchanged. It may not be possible to fall below the fixed price, and the appraisal value may not go down.