Gone with the wind. Er weight.
The Cottonwood passed its time in history. The problem is the cottonwood would only hold 250 lbs of weight plus accessory weight. Most modern tree stands now hold 300 and 350 lbs.
With its design the weight of the stand was around 21 lbs. With added holding weight, the treestand would be in the range of 30 lbs. , unfortunately too heavy for modern climbers.
Most modern climbers need the 300 or 350 weight limit. The modern design makes it unneccessary to make it merely for lighter hunters. It standardizes everything. It standardizes production.