It just means that nobody bid at the sheriff’s auction on that property.

The mortgage company that foreclosed will normally set a Reserve (or minimum price) they will take at the auction. If nobody buys it for that price, ownership reverts to the mortgage company for that price and then the mortgage company has to sell it through conventional channels (listing it via a realtor).

So the mortgage company isn’t really “buying” these properties. They’re just getting stuck with them because nobody else will buy them.

When a house is foreclosed on and the bids are not high enough the mortgage company will buy it back so they can list it themselves. This is very common.