Some people insist that providing slippers is a must by pointing out the example of Japan:
In Japan, you are not expected to go bare foot; the host will always give you slippers.
This is actually an half-truth. It is true that hosts will normally provide slippers in Japanese homes. However, these are intend to be worn in the hallway and kitchen. Bedrooms and living rooms normally have tatami (grass mat) flooring. It is expected that one removes slippers and step on the tatami in either stocking or bare feet.
Carpet has become more common in Japan and often it is expected that one removes slippers even before stepping into carpeted rooms.