I would think a department store salesperson would know more about the products in the department they are working in than the consumer would, but......... Some sales people know everything, or very close to everything, about the products in their department and that was one reason they were hired to work, or manage, the department. OTOH, many don't. You are looking for a new digital camera and you ask the sales person a question about a certain digital camera and the sales person replies "I really don't know". Or, the sales person says something about the camera that is very different than you read about online. I bought all of my horse tack, feed, western clothes and rodeo stuff from two different stores in So. California. One was called Norco Ranch Outfitters and the other was called Broken Horn. Not one single employee, at either store, had a problem answering any horse, western clothing or rodeo question I asked. Now, most Boot Barns, and even the JAX Farm & Ranch Equipment store across the street from us, haven't got a clue about professional rodeo. The sell ropes, but, basically know nothing about the type of ropes they sell. So, if a beginner roper goes into JAX, looking for a brand/type of rope, they'd better be knowledgeable about what they are looking for! As for myself, I like to ask a sales person a question about a product, they tell me and then say, "need anymore help?"
Retail people are placed where needed, not where they always have the most knowledge. Sometimes you can hire a person that is knowledgeable and needed in that area- that is every managers dream. @Cody Fousnaugh , but I do understand your frustration.
I think that may be one of the differences between shopping for electronics in an electronics store versus a more generic big-box store. Given that people who work at these stores probably don't plan on making a career of it, except perhaps for the managers, they are unlikely to be familiar with each of the large number of products these stores carry. On the other hand, if you were to shop for a camera in a camera store, you'd probably have to pay more for the camera but you'd be more likely to find someone who knows the products.
The sales guy at Best Buy who sold me my laptop seemed to be a college aged computer geek, at least that was my impression.
As more people buy from the internet, the quality of the in-store service will continue to decline. People who are smart and knowledgeable will go where they can earn a decent living. When folks come in, pick their brains, then go buy on the web, salespeople make no commission. So they go into another field and they take their brains with them. Heck, you're lucky to find a store these days.