I always always always have at least one with me, and have for years. Now and then I do an "emergency reading" for someone, but mostly it's there to keep me company.......and sometimes to while away waiting time, or study. The deck is chosen pretty much daily, because it's new, or I want to study it, or feel especially drawn to it that day.
When it's 2 or 3 decks, one is meant to read for others with, one is meant to study, and the last is for looking through and bonding with--usually the newest deck in the house.