I would assume what you are saying is correct, but I don't have weight distribution bars, and I don't feel the need to have them. When I first lowered the BP down on the Escalade it looked like I was going to have to get them until the pump kicked on. Before anyone ask the Escalade with a 6.0 liter handles the 3 horse, all steel Titan Avalanche trailer, loaded with 2 real horses,1000 lb a piece and a 600lb. pony with no problems. My wife drives it with no issues at all. 

 so basically what i'm hearing is that the components are not strong enough to carry the load so the air bag fills up to hold it up?

Not necessarily.  The air bag is adjusted to keep the vehicle level while loaded, but reduces air pressure when empty for a "better" ride.  Just because the air pump needs to kick on doesn't mean the vehicle isn't designed to carry the weight.  It's no different than putting air bags or timebran(sp?) springs on a truck to keep the ride smooth while empty but level while loaded.

The Escalade is equipped with a towing package and has a tow rating of 8,100 lbs., We are well within those numbers.

You are not wrong.  "What" you are, is overlooking the fact a 1/2 ton (pickup or suv) does not need WDH for ~600# tongue weight.  Just because it squats down more does not indicate more weight transfer.  Take the softly sprung suv drop the 600# on the ball and it may squat 6"......the springs are meant for comfort.  Take the same 600# drop it on a pickup and it may squat 3"........the springs are meant to carry a load.   In both examples, assuming similar wheelbase and overhang, the same amount of weight is removed from the front axle.  A WDH can lift the rear of a softly sprung vehicle without necessarily "distributing" weight, the same as air bag suspensions.

A WDH is all about leverage.  With the trailer in my sig (~900# tongue) hooked to the Trailblazer I NEEDED a WDH.  Something like 400# was removed from the front axles 2400#.  With the wheelbase and low vehicle weight of the Trailblazer hitched without the WDH the F/R distribution was 36% F  64% R......made for lousy handling.  A WDH returned the weight to the front axle and restored the handling.  Same trailer on the new 3/4 ton Dmax does not require a WDH as more front axle weight to start with means less % of weight moved to the rear.

Most over the road tractor trailers use air bag suspensions.  It has nothing to do with being "strong enough", they still have their axle ratings......with air bags they simply dont squat like a conventional spring suspension.  There  is nothing "scary" about towing with a suv, Lexus or otherwise.  Fear of towing with an suv is a silly and antiquated notion, nearly ALL modern midsize (let alone a full size) suvs are capable of safely towing a 2h BP......the driver is another matter.

It's real funny I was talking with a guy the other day about this same stuff, I remember well loading up my 1967 Chevrolet 1/2 ton truck with 3,200 lbs of tobacco and taking it to market, I was really proud that day because also along for that trip that day was my father in his half ton 1974(new) 4 wheel drive truck, he had 2,800lbs. and my grandfather with his 1973 1/2 ton pick-up he had 2,600lbs. The real kicker to this story is I was 17 years old, the tobacco warehouse was 40 miles from home. I can still feel how light the front end was on that old truck. In todays world everyone would want to put my dad in jail for letting a 17 year old make that trip. In my world, I was not the only 17 year old driving to the warehouse that day.

Times change and so does the thinking about what is right and what is wrong. Today in my state you don't even get to drive until you are almost 17, everyone on the internet thinks you have to have a Crew Cab Dually to pull a trailer, I say I would rather have my wife in her Escalade pulling 6,500 lbs. than alot of men I see pulling 2,000 lbs. with a CC dually.

I was raised on a farm and had been driving since I was 12, working for my dad in fields, dealing with farm workers, and doing as I was told, my dad knew exactly what he was doing when he put a few extra pounds on "MY" truck.

Close enough for this forum discussion. We appear to be in the same ballpark.