Well, that "Ladder of Loyalty" makes it pretty clear why a street-smart, savvy business will realise that a prospect is not commercially deserving of much courtesy.
Not at all. The business needs to be courteous to everybody because it is trying to move them up the ladder. Trying to turn a prospect into a customer/client and so on up the ladder.
But what it does tell you is that a loyal client, or supporter, or advocate deserves the loyalty of the business in return - indeed they are entitled to expect it.
That means that if I'm standing at the reception desk of the flight school in a ten minute break and two people arrive at the same time to speak to me, one is a stranger and one is a student half way through their training lets say, then spending time talking to the stranger because they might just possibly become a student while I ignore the existing student because I've already got their business and it doesn't matter if I fob them off - is wrong. WRONG.
What I should do is quickly find out what the stranger wants and then politely ask them to come back another time, or whatever is most appropriate, so that I can deal with the issue that the existing student wants to raise. Because they have paid for my loyalty to them.
I do not understand how this is being discourteous to anybody.