They're going by conjecture and out dated information, and plain old fashioned yeast fear. Or they're just idiots....You'll find that not every proprieter reads every forum or book or listens to every podcast, so the last book or info they may have learned may be in Papazian from 30 years ago. They also may only brew kits. Or simply JUST be of the "you can't teach an old dog new tricks" mentality.
But not every person, especially one of those "you can't teach an old dog" types aren't going to be up on the latest ideas.
Remember to a lot of LHBS'er or employees, it is only a job..not an obsession...so they are not always as necessarily passionate, or zealous learning new things, or trying new techniques, like we are....SOme even though they have been in the business forever, may never had progressed in the hobby beyond extract kits...some may rarely brew at all.
So often it is not surprising that we know more or are at least in touch with more info that someone who does it for a living....
This is an ever evolving hobby...Places like this is where you find the most state of the art information/wisdom about brewing, because of the sheer number of us trying new things, hearing new things, and even breaking new ground and contributing to the body of info on the hobby...Look at some of that inventions that came out of here, and then ended up later in BYO articles by our members...
It is podcasts and forums like this where you will find a lot more state of the art, or current views, and even scientific information...I mean if Jamil, John Palmer or Papazian even farts on a podcast, one of us beergeeks are going to start a thread on it within 10 minutes.
Remember- It is HUMAN nature to scorn that which we don't understand... It even happens on here sometimes, when someone attempt to break new ground, or suggest something different from common wisdom (we still get people who scorn the idea of long primaries, and still believe in autolysis)...but it really is not the norm here.
But not necessarily "out there" in the world of Home brew shops.
You'll find that more and more recipes these days do not advocate moving to a secondary at all, but mention primary for a month, which is starting to reflect the shift in brewing culture that has occurred in the last 4 years, MOSTLY because of many of us on here, skipping secondary, opting for longer primaries, and writing about it. Recipes in BYO have begun stating that in their magazine. I remember the "scandal" it caused i the letters to the editor's section a month later, it was just like how it was here when we began discussing it, except a lot more civil than it was here. But after the Byo/Basic brewing experiment, they started reflecting it in their recipes.
You will find that all the information you need to understand that topic and to have ALL your questions answered is here, there really is nothing on the topic that hasnlt been covered in this thread.
To secondary or not.....
FYI Last week I finally bottled the chocolate mole porter that I brewed on 5-27-10. I had car issues and then health issues and other things that prevented me from getting around to it til last night.
SO it is nearly 5 months old. And it tastes amazing, and is crystal clear (at least as clear as a jet black beer can be) and tastes perfect. No off flavors or aromas whatsoever.
I don't think I've ever had a beer that was so clear...and the yeast cake was so tight that it was like concrete in the bottom, and I racked off what appeared to be the entire 5 gallons of liquid, and almost no sediment or hops.
I'll know more in a month when it's carbed and conditioned, but I think it is going to be perfect when it is done. I'll have some BJCp judge friends blind taste it to see. But I don't think there is a hint of "autolysis" or other nasty nonsense in there.
There's enough info on here, in BYO magazine and on Basic brewing to back this stuff up...None of their arguments really hold much water anymore. They're about 5 years and several brewer's medals (even mine) behind the times.