I've stayed in local hotels in Japan that provide very substantial leather slippers. To me, this fits with the traditional restaurants in Japan that have the toilet slippers provided for guests to use. In those cases, the slippers seem to be communal and not sanitized.

In Rio, hotels tend to provide flip flops for guests to use in place of slippers. These are rubber or plastic and presumably could be sanitized for the next guest, although one place told me very pointedly that they were a gift to take as a souvenir since everyone in Rio lives in flip flops. [I didn't as they weren't comfortable for me.]

OTOH, ICN provides slippers at their security checkpoint for people who need to send their shoes through the X-ray machine. They are very prominently signposted as having been sanitized.

This reminds me a bit of the rental bowling shoes that are advertised as being sanitized between use.