@Jeff Copeland
If the listing agent disclosed all information on the property when it was listed then there would be no need to contact listing agents. Also how is it unprofessional to call and ask a few simple questions that should be regularly available to the agent.
You're saying that if I called a business and got to talk to the secretary, that it would be unprofessional for me to ask that secretary some questions, and that having a secretary tell me that I need to have my secretary call them to get information seems like a reasonable practice?
Real Estate agents are not needed to buy and sell property, there is no laws requiring the use of an agent (To answer you example in italics, yes I would contact the defendants lawyer to get information if my lawyer wasn't doing their job also, also because of disclosure of information in a legal case I wouldn't need to contact the other lawyer.)
Agents don't normally work with one person at a time so bugging an agent for every little property that is missing information seems like a huge waste of time. So there are multiple benefits to contacting the listing agent directly, 1 I don't flood my agent with petty questions, 2 It is much quicker to ask the questions that are missing from the listing. 3 I can tailor specific questions per property. 4 There is no back and forth which limits misunderstandings.