A beginner going into a bike shop likely doesn't know what he wants anyway, so it's up to the LBS to convince him that he should go for a particular bike given his budget. Very often he ends up blowing that budget anyway. He's probably not going to know what to look for on a test ride anyway. Do you think a beginner rider can go for a 20-mile test ride? The upside is that he's likely going get a bike that fits him well.

BF types going into an LBS to buy a bike likely knows exactly what bike he wants and what size and what price he's willing to pay for it. If the LBS doesn't have what he's looking for he'll go to another one that does.