I workout hard at the gym I'm training for like 6 months now and I am wondering why do I never have muscle soreness at my back, I workout very hard, after every training my arms, chest, feet every muscle group suffer muscle soreness except my back, and I really train it until exhaustion until I cannot go any further but nothing. Do not get me wrong I see improvements, a lot of them and my back muscles are a lot more developed than from the start of my training but I never had muscle soreness on it and I am wondering why?
DOMS (delayed onset muscle soreness) is primarily something you feel when you stretch out the eccentric portion of the exercise.
The soreness is caused by eccentric exercise, that is, exercise consisting of eccentric (lengthening) contractions of the muscle
The "eccentric portion" refers to when you lower the weight.
If you're not feeling any DOMS in your back, it could be because you're lowering the weight too quickly. Try instead to lower it slowly and controlled. Remember that this portion of the lift also helps with muscle growth.
As a rule of thumb, I try to lower the weight over twice as much time as the actual lift. So for instance, I'll spend 2 seconds lifting the weight, and 4 seconds putting it back. Rinse and repeat.
Anecdotally, this has always provided me with that amazing DOMS the next day.
Per your request in your comments, I'd refer you to my answer to a similar question pertaining to ab training. As I indicated in the answer from the referenced post, DOMS is not a valid indicator of progress or muscle growth. Studies have shown that there's no causal relationship between DOMS/EIMD and muscle hypertrophy or "progress". You should look for a more reliable indicator for your training progress. Progress should be based on whatever you've decided on for a goal.