This is a really rapid read to suite those on the move. The infographic below answers the question in the title. The answer applies more to the old-fashioned but still current way of allowing cats outside unsupervised in many countries where they will scent mark their home range. If a cat is indoors full-time their home range is inside the home and they are less likely to routinely scent mark as there is no competition from other cats who scent mark over their scent marking (their ‘calling card’).
In multi-cat homes where they are all inside all the time, there might be some scent marking over furnishings but the cat share a very compressed home range which overlaps and which forces them to compromise and suppress their natural instincts. But pressures can build up. However, when several cats are full-time indoor cats without any mental stimulation they tend to shut down and they lose their drive to scent mark or indeed, in some homes, to do anything other than sleep.
