I have a very particular view of pitchs.
The other day, on my former job, I had a meeting with wery important CEOs. I had already quit my job and the meeting was to explain my decision, as these CEOs were important clients and I used to handle the contact. Explaining that I decided to move on and go full-time on my startup they casually asked "what your startup was about"? There it is! THIS is the pitch that matters. In two or three phrases be able to explain what it is, my vision of it and make that vision stays in their heads so, at some convenient moment, they will remember me.
Not just because they were important CEO, this pitch is important so every founder must have it ready, by heart, without thinking, to present his idea do friends - so they understand and support you; to your father - so he doesn't tell you to get a job; to other founders and developers - in order to create a relevant network. The "nay-sayers" are just a result of a bad pitch.
This pitch is very important. Is must go out with any thought, automatically. You only need two answers: a initial one, of about three phrases and a complementary one, if the interlocutor become more interested and give you space to evolve your answer. More than that is a conversation, not a pitch.

Do you know for who you don't need any pitch? Investors. I don't say potential investors, people that someday may remember you and decide do invest somehow (as the CEOs I mentioned before). No, I am talking about that meeting with interested investor, face to face, when you are there only to present your startup and he is there only to decide whether they will invest or not on you. A meeting is a conversation, not a pitch. It is the moment where you tell them what do you know, not what you have memorized. You must listen to the investors, understand their doubts, it demands a lot of empathy. Before a meeting like this you must prepare your knowledge, not your speech. Any PPT is only needed if you must show important, complex and specific data ( therefore, not worthy of memorizing).

Something different are startups events. To start with, I think these presentations on startup events are highly overestimated. In general, they exist more to promote the event itself (and the brand of the organizer) than to make your startup any good. Events are great for networking, learn new things, discover different opinions, but not for pitchs. The only exceptions are accelerators' demo days, but even so, I would guess that most investors go into these ocasions already briefed about whom they will talk to. But some serendipity may occur. These kind of pitch are more focused on memory than knowledge. Q&As at the end of your pitch are always more about mistakes or absences on your presentation than about investment decision doubts.

I don't want to rebel against the system here. I only think that "pitch" is a twisted concept these days. Too much influence on it of media, ego and vanities. In summary I think two things are essential: i) you must have a very memorized pitch, as a standard first answer, ready to go out without any further thought, to anyone who ask you what is your startup about - something clear, short and visionary at the same time, to show the idea and attract interest and ii) you must not have anything memorized when this initial pitch becomes and actual convesation, but, for sure, be deeply updated about all the knowledge that involves your startup.