Because you are likely spending thousands of dollars a year on hunting, out of state trips, preference points, maybe access or habitat improvements, gas, etc and rifle scopes are a well documented failure point. Why cut corners on a scope that risks that money, time and effort? A $1,000 scope is going to have a useful life of a decade or more, it will save wasted ammo, range time that could be used for training or otherwise. It also might save a backcountry hunt when a lesser scope might have otherwise failed.
Being able to understand things that cost a lot of money but provide great value is what we are talking about here.
The argument that someone is a successful hunter in spite of using a cheap scope isn’t really a fair comparison. In 90% of the US being a well connected, socially charismatic, rural based person in the agricultural, real estate or forestry fields will gain you access to low pressure animals that can be shot at close range.