Here's the thing though. When rod manufacturers design and build a rod, they don't know how each person will be fishing the rod, under what conditions, etc,, etc., etc.
SO, they have to pick SOME sweet spot, and they do know that a "trout rod" is more than likely going to be fished somewhere between 20 and 40 feet. So, they pick a weight against the flex in the rod at 30 feet of line given the rod's weight of line designation and assuming that weight of line is used.
You an defeat this by under-weighting the line for the rod, or overweighting to adjust that sweet spot for your particular normal casting distances.
This is not to say that it won't cast just fine and shorter or longer distances. It is just that they have to pick one for the rod design.....