You seem to be making some assumptions based solely on the fact that the author didn't like the sales people he was working with. He never elaborated on the rea

You seem to be making some assumptions based solely on the fact that the author didn't like the sales people he was working with. He never elaborated on the reasons. But I can foresee many. For instance, it is possible that the culture in the company encourages certain types of sales people, while it turns off others. Take the previous paragraph and replace "sales people" with "programmers". You can see that the same applies. It has nothing to do with introversion/extroversion. On that matter, the usual stereotype of the ultra extroverted salesman that is incredibly successful is pure bollocks. Being extroverted doesn't build you a thick skin to be manhandled over the phone, experience and repetition does. As well, being introverted doesn't mean that if you have a bad conversation, you'll crawl back under the sheets for the rest of the day. You're either misunderstanding extroversion/introversion or you're misunderstanding sales, or maybe both. I'm currently a programmer and entrepreneur and in the past I've worked as a salesman without formal training. I've had phone sales jobs (phone plans), street sales jobs (random knick-knacks) and store sales jobs (men clothes). Only recently, after coming to the same realizations than OP, I've decided to formally understand Sales as a profession, to help me promote my services and software. I've been studying it for a few months and am convinced that most people misunderstand what selling is. We often like to imagine slick, silver-tongued, extroverted people, with poor ethics. This is only a partial truth. After all, sales is one of the few professions where money is directly tied to performance. It shouldn't come as a surprise that poor ethics be prevalent, it's the easy way out. But it does in no way constitute a requirement to be a good salesman. Most successful salesmen I've observed are unequivocal about ethics, they discourage dabbling in shady practices. I've also noted that a good number could in fact pass for introverts. My understanding so far is that even extroverts need to tap into their inner introvert at some point, if they ever want to become good sales people. Being extroverted might help in approaching people in random social contexts, but introversion helps to align oneself with the needs of potential clients, because it helps in observing and listening to what your prospect is trying to tell you. Whether introvert or extrovert, anyone can learn to act accordingly when the situation demands it. All this to say that selling is a skill and can get very methodical and technical. Like any skill, anyone can learn it.