They are likely to use them as unintentional littler boxes.
Rabbits do like a hidey-hole of some kind, but you’re better off turning that box upside down so they can hide under it instead of jumping into it. Lots less cleaning, which means healthier rabbits.
Genius is 1% inspiration and 99% perspiration --Thomas Edison ... sweaty tiny ad:
Escape to gardens and natural buildings (for free-ish) in Montana