It's all up to personal preference. Maybe they hunt in open enough areas that a couple more inches doesn't make a difference. Why do some people shoot bows with ATA @ 40+" when they could shoot a shorter ATA like 33"? It's all personal preference.

Also, if you take 2 stabilzers with the same weight, say 10 oz, but one is 5" and the other is 8"...there will be a difference in the balance of the bow. The longer stabilizer will put the balance point more to the front, while the shorter one will be further back. If there is a lot of weight towards the rear of the bow initially, then a longer stabilizer will help to pull the balance point forward quicker with a lighter stabilizer. With a shorter stabilzer, you would need to add more weight, thus making your bow heavier.