Let me put it this way. Commuting is something you do on most days and if you decide to do it by bike it is easy to make it a habit. Making a habit out of running errands on your bike is harder to do if there is only the occasional errand to run within biking distance. Lots of people run their errands going to and from work.
Another problem is that although suburbs are getting better about this than they used to be, zoning is often such that residential and retail areas are separated. There's not always that many destinations within easy cycling distance anyway. Speed limits are higher and the infrastructure isn't there to make it all that appealing to bike, other than recreationally.
As for the premise of the article, while I wouldn't say that commuting by bike is a bad goal, I think it is an unrealistic one for a good number of people. If the real goal is to get people to drive less or use less fossil fuels then other alternatives to cycling should be explored (and they are). And sure, people should be encouraged to walk or bike more for short distance trips whether it's to work or not.
I also have to say that I'm a little bothered by the tone of the article in places:
There’s also a perception problem. Have you noticed what the average long-distance bicycle commuter looks like? Good luck convincing your neighbors that what they want to do is invest thousands of dollars in special clothing, spend time every morning putting those things on, and then, GO OUT IN PUBLIC.
Really? Thousands of dollars?
As I've said before, what the Dutch have done is enviable but I think bike commuting under harsher conditions and for longer distances is a worthy goal for a reasonable number of people even if it's not the majority. To accomplish that will mean taking some different approaches from the Dutch.
FWIW even they are trying to encourage people to ride longer distances by investing in "Super Highways" for bikes.