Why Truck Camper need a air bag? Do I really need it?

Personally would not want air bags anymore. I added upper Torklift stable loads on my ram which helped a lot with squat. Might add a swaybar. TC is over 4000 wet.

We have the 2014 Ram dually. Just added upper Stableloads and Timbrens on back. Works great. No need for airbags.
Hope you have/are getting Torklift tiedowns.

Air bags can be for left/right balance but are usually primarily to allow you to adjust the stiffness of your suspension. I have them on my dually, I just dial up the pressure when loaded and turn it down when empty, no need to drive around getting jarred by permanently-stiff springs.

Thanks.

Yes, the pickup is a dually

So, airbags are for balance between left and right?

Presuming dually.
If you have doubts, haul it home with nothing for suspension mods. Truck will handle it fine but might be squatting more than you like. Then decide what you need for the back end.

My short answer is probably not. Air bags typically help pick up an overloaded truck to return it to a level (normal ) ride position. There are cheaper ways to do that by better utilizing the overload springs by using longer overload bumpers or other more engineered and expensive solutions.

I think you would be better to spend the money on upgraded shocks and a anti-sway bar. Our last truck was a 2004 Dodge Ram 3500 that we loaded a comparably heavy camper on. I did have airbags but mostly to help control the imbalance of weight due to the full wall slide. The truck did carry the load ok without them.

In any case you should have plenty of stock truck to load it and get it home to further evaluate.