When is it useful to use the kiln?
With our middle European climate, the moisture content ends up averaging around 15-20%. Even in 100 years, it probably wouldn't be any drier.
Apartments with central heating have dry air with a moisture content of around 6-10%. Floor boards which have only been air-dried would lose the last bit of moisture, shrink a little and create gaps. In this situation it is useful to rest dry the boards in a kiln before installing the floor. However the natural drying process should have been finalized before the kiln.