Cat experts tend to recommend that the number of litterboxes a cat-owning family have in the house should be equal to x + 1, where x=the number of cats you have on hand at any given time.  We have two cats, and are rule-following, equation-loving, cat-expert-respecting people, so we have three litterboxes.  Two of them are located in bathrooms (partially due to the fact that bathrooms are already theoretically kind of icky so we’re less concerned about the far flung tracking of little tiny bits of litter by little tiny feet, but mostly because there just is no good place to store something like a box full of multi-cat formula, odour-fighting, dust-free clumping gravel) and I’m always surprised by the frequency with which I enter a bathroom and already find it occupied by a cat, focused intently on doing the exact thing I was just planning to do.  I am even MORE surprised that my natural reaction is not to ignore the cat and stick with the original plan, but rather to apologize to the cat and sheepishly back out of the bathroom.