The usage rates are vastly different. What do people in an office building use water for? Coffee, dishwashing, toilet flushing. Those will be somewhat dispersed through the day. Compared to a residential building where half of the building is having a shower in the space of an hour or so in the morning. So you need to get more water in and more water out, both of which probably need the pipes replaced, and more space to hold them (even more at the lower levels of the building). Similar problem with electricity if that's what's being used for cooking.