Why should I write a good undergraduate thesis? I am nearing the end of a semester-long bachelor thesis in computer science. My supervisor suggested I set aside the last month (around 20 working days) for actually writing the thesis document. As such, I have begun this period now.

Why is a thesis important?

Given limited time, I am confused as to why I need to write a good thesis. I am not against writing it, I just want to understand why a good thesis is important so that I can optimize my time accordingly and focus on the important sections.

For instance, if I were writing a paper for a conference, my goal would be to convince potential reviewers (as well as the research community in general) about the merit of my proposed ideas and their novel contributions. As such, I know the intended audience and the intended message for such a paper. Along these lines, who is the intended audience and what is the intended message for a bachelor thesis? Firstly, I doubt many would be interested in reading a bachelor thesis, so this confuses me when I think about who I am writing this thesis for. Secondly, should I consider the intended message as convincing the reader of my ideas, in which case the thesis essentially becomes a long research paper?

I am dealing with these questions because I've found that I can write better and more persuasive matter when I think from the reader's point of view with a clear message to convey to him/her. But currently, I am neither clear about the audience nor about the point to make with my thesis.

I spoke to my supervisor about this. He said the thesis document is a report of all the research activities I did during the time allotted for it, which includes all experiments irrespective of their results. In contrast, a research paper focuses on one method which worked very well. With this in mind, one could say that the intent of my thesis is to inform, so that all experiments (with positive or negative results) serve as some kind of knowledge contribution to the research community. However, this still leaves the question of who the reader is, what should I assume about them, etc.

Which sections are the most important in my thesis?

Part of the reason for asking the former question is to obtain an answer for this question. Which sections are the most important in a thesis and why? From my understanding, the sections which stand out (like the abstract, introduction and conclusion) are the most important as they're the most likely to be read by potential thesis examiners, peers, etc.

Is there any other section that I should especially focus on?
The audience
The correct, but somewhat cynical answer is that the main audience for a thesis or dissertation is the examiners. They'll have to grade it (or at least sign off on it), so you want to convince them to give you the grade you want. The next audience you'll want to target is actually yourself.
Some years from now you'll have forgotten some of the details. You can try to track them down again, but if you've written stuff down in a format that's helpful to you it's going to be a lot quicker and less painful. Basically, if you write the document well it can be a great reference. (I admittedly haven't opened my bachelor thesis many times, but I looked something up in my Masters thesis just yesterday.) Sometimes the thesis can also be useful for students doing their projects on the same topic, in the same research group, etc.
The other big point is that writing the thesis is supposed to be practice for future writing of e.g. dissertations or papers.
What sections are most important?
From the practice angle, all of them. To convince your examiners, probably introduction, results and conclusions - but different people will have different priorities. However, it's a case where you have a few people who are supposed to read your thesis, so an excellent abstract is less important than in a research paper. Basically, you want to show that you understand the field, and have done good work.