As a movement therapist, I sometimes see young children continue to walk with their heels off the floor.  Some of these children may in essence be delaying their development, or demonstrating a subtle difficulty in coming "down to earth".  I agree to check with the pediatrician to see if the child's early reflexes are integrating well as they should, and if the child's sensory system, including touch and balance, are at age level. I would also give lots of opportunity for the foot to develop a love of the feel of the earth underneath, by walking on different pleasant and safe surfaces - sand, mud, shallow water, both in well-fitting shoes and in bare feet.