They aren't devoid.
Your "zodiac sign" is actually ONLY your Sun's sign .. one of 10 "planets" used in asterology.
Sun indicates ONLY how we try to feel whole inside. When someone has Sun in Aquarius, they try to be logical, rational, detached because THAT is how they find a sense of inner wholeness/rightness.
MOON is their emotional nature, not Sun. And everyone has emotions. What varies from person to person is (1) how much we hide/show our emotions, and (2) how well/poorly we work with our inner emotional responses.
Always look to their Moon for clues about their emotions. And the Moon sign can ONLY be found by doing up the personal birthchart (full birthdate, exact time, place of birth). Moon can be in ANY Sign, since it only takes 28 days to move through all 12 Signs.
Mercury is our mind, Venus is how we relate, Mars is how we take action, etc.