Pam - I agree with you to a degree, as the best horticulturists I know are landscapers. However, to become an LA one has to undergo a rigorous training that virtually assures they know a little about a lot of stuff, and lot about some stuff. I agree that in general these folks are horticulturally, botanically, and ecologically challenged -but they have had the benefit of some training in soils, plant science, plant ID, IPM, etc.
However, to be a landscaper (in most places and at most times) one has to have a pick up truck, a shovel, a mower, and some gumption - formal training of any sort be damned. No flames here please - I have billed myself as a landscaper for a portion of my career.
I know there are tons of exceptions, but after nearly 20 years at this these are my opinions today.