All this depends on your weight, how fast you ride, 2up yes/no, luggage.
I am super heavy (255lbs/115Kg). To be honest, not a lot of people of my size ride that fast in the dirt so I can't blame Honda for not having a Sumo wrestler as a test rider for their bikes
At least offroad I ride pretty fast, especially for a guy in my weight class. Furthermore I love to ride 2up with my wife (glad that she is below 100lbs). Oh yes, and I have always at least 20lbs+ of luggage with me. So this is a lot of weight and a closer look to the Honda instruction manual tells me I am super close to the maximum weight capacity of 392lbs/178Kg.
Surprisingly the AT is not unridable like this, but for sure it is impossible to get the sag setting right with the stock springs. There is no way to adjust without different springs. So this is an upgrade I will do some day. Not sure if I should just change the spring or directly get a better rear shock also. Maybe I should wait a bit longer, and when my rear shock gets weaker I can replace it with something better.
However, for someone with a weight between 155lbs(70Kg) up to 200lbs (90Kg) who mainly rides not 2 up I don't see a problem with the standart springs. But with luggage AND 2up even these people will not have the pefect sag setting.
P.S.: It is midnight here and just because I wrote this, I will go now to the gym to try to loose some weight. This is the best and cheapest suspension upgrade on the market