Here's why:
* No Sensory Organs: Transformers are primarily robotic beings, and their bodies are designed for combat and energy manipulation, not biological functions like smell.
* Focus on Technology: The movies focus on the Transformers' advanced technology and their battles, rather than exploring their senses.
* No Mention in the Story: There is no mention in the movie or its lore that Transformers have a sense of smell, nor are there any scenes that would imply such a capability.
So, while Transformers can see, hear, and communicate, smelling is not one of their abilities.