Why Can't I Buy This?

Here's a thought that might need some clarification... I've sold a few things in my career. The majority of my sales have been devoted in the wireless phone industry (cell phones & service, etc.). Something that comes up quite frequently is when I client wants to buy something but the sales rep won't sell it to them for some crazy reason.

While this seems odd, let me point to the sales rep thought process as this may explain things. 

As a sales rep--especially a commissioned one--it behooves them to make as many sales a possible to earn money, correct? If that's the case, if the sale rep is intentionally not selling you something, then there's very likely some logical reason behind it, and 9 times out of 10, it's something that the rep has zero control over. These might include:
(1) customer's not eligible for that product or service for some reason (credit, tenure, policy, etc.)
(2) in the case of accounts, that client talking to the sales person is not authorized to make changes to that account (very common if one spouse is the actual account holder and that spouse is not the one talking to the sales rep and with business accounts)
(3) the product or service you're requesting is a piece of crap (there are differing opinions on whether a sales person should actually mention this...I'll reserve that topic for another post.)

 With that in mind, 9 times out of 10, that sales rep who intentionally won't sell you something isn't being a jerk, just like he/she is not intentionally trying to not make money; they simply can't sell it to you.