It is a pretty common phenomenon that parents continue to live in their single family home long after all the children has moved out. At least in Sweden this is definitely the case. Not really a lack of single family homes, but too much friction for people to move to a more fitting home.
I'm referencing the 2M+ short term rentals in the US. Obviously not all of them are but let's just say more than half. That's a lot of inventory sucked off the market. More than double the total number for sale right now.