Why do proturans use their front legs as sensory organs?

Proturans lack antennae, which are the primary sensory structures found in most other insects. To compensate for this absence, they utilize their anterior pair of legs as specialized tactile organs.123

These front legs are held above the head and are equipped with sensory organs located on the anterior tarsus. By positioning these limbs forward, proturans are able to navigate their environment and detect stimuli in a manner analogous to how other arthropods use antennae. While they possess three pairs of legs, they rely exclusively on their middle and posterior pairs for locomotion, leaving the front pair free to function as dedicated sensory appendages.1234