I have had this happen in the past with veilds, in particular. I hand feed about 90% of the insects, mos tof the time.
Veilds are more agrresive, and they come right up to you to eat.
None of my veilds ever failed to do this, they streatch out right to me every time I hand feed, getting as close as possible. Every other specie sI have worked with was much more "typical" sit still, and use the tongue's full capability.
The deremensis seem to be the most dependable.
My veilds will practically try to grab an insect out of my hand with their jaws. If I put bugs in a bowl for my big male, he goes into it, and snaps them up with his tongue like a bearded dragon, not shooting it at all. I have to "force" him to shoot his tongue, by holding the insects far away from him. He will hold onto a branch with his tail and back legs, only after stretching out a foot from the branch will he shoot his tongue. If I free roam, he runs them down and snaps them up. Only with hand feeding does he get tongue excercise.
The deremensis are simply too lazy to get up and move. Not really, that's just how they are--stealthy. My 15" female routienly shoots her tongue 18" out--I've never seen such a proportionally long tongue in a chameleon. First time I saw it I was amazed. I had a big bowl of crickets and superworms on the ground of her enclosure, and I was picking up some to hand feed her when I saw it happen. I never thought she could have reached from her perch.
My little male wouldn't eat from my hands for a while, so I had to bowl feed him, using the plastic milk gallon cut in half method. Deremensis learn to sit by their bowls, and go nowhere else. as a result he's had a bit of a lazy tongue. Thankfully, he's now eating from my hand, so I have improved things a bit for him recently.