Most Helpful Guy
Depends what you are talking about - Sniffing a random girls hair on public transport creepy but in a loving situation, some men like the feel of a womans hair and the scent of her shampoo - Would be the same as kissing a womans neck and noticing her perfume.
Most Helpful Girl
As a matter of fact they do.
Why? Because they can't help it! It is biological.
Your body naturally emits pheromones. Pheromones play a crucial role in human behavior, including the mating process.
Human-beings are animals with developed self-awareness and logic (ha-ha). We are mammals and well, mammals are guided by their noses.
We react to certain odors and we subconsciously determine compatibility or incompatibility with other human-beings based on their scent.