I'm not Pete, and I didn't stay at a Holiday Inn either, but you have already answered your own question in a backhanded sort of way.
First, there is no adjustment on the stock suspension other than rear spring preload. Therefore, we are asking the design to deliver satisfactory ride and handling with a wide variety of load. Few of us are 'average'. Many load the bike up to the approved gross weight or beyond and take off across the country. Other days, the bags are empty and we ride out to attack some twisties. This group has a tendency to do both of the above at the same time; I know I do. A suspension that is designed for the 'average' just cannot cope with this range of performance as well as quality tunable suspension, properly setup for the conditions.
Damping rates for the stock shocks are fixed, and as I mentioned, the conditions are definitely not! Considering the diverse loads we impose on them, they do a reasonably good job. Quality adjustable suspension offers a range of performance that the stock equipment just can't deliver.
All this means is that good aftermarket suspension can be set to provide the performance envelope that YOU use, not the average Joe. That's the reason you see sportbikes with multitudes of adjustments straight from the factory along with sections in the owner's manual on how to set it for your riding style. A lot of people never adjust their suspension and don't get to realize the potential of their machine. BMW knows this, and they have an answer: ESA, which I'll bet will be available on every new model from now on.
Once you've ridden a well setup bike, you'll never go back! They provide a smoother ride, transition quicker, and provide a level of confidence that will let you exploit the machine to its potential. The chances of getting the theoretical 'optimal' performance from the stock suspension are a lot smaller.
When your stock parts wear out, try some Wilber's or Ohlins. It is definitely worth the money.