The goal of a PhD is to make a contribution to the body of human research. This involves, not only doing the actual research, but reporting it, too. And it can involve verifying the research of others, because any real research should be verified by peer review.
Writing publications is the process by which research is reviewed and reported. A series of smaller publications is less risky than one big one, especially for a new researcher, but it is not unheard of to present all the work from your thesis in a single peer reviewed publication.
You cannot always do research in a vacuum. At the end, to have impact, someone must at least read the research. Your PhD will be judged on your novel contributions to your field and these will be that much stronger if they are peer reviewed and published (or in the process of such).
The aim of a PhD is to make a contribution to research. It is more than having papers submitted (accepted), your papers should report the results of your research so your peers can review your contributions. Peer review will validate your contributions, ensuring their significance and correctness (or plausibility). It is YOUR research and it will result in YOUR thesis and YOUR contribution (or publication list). But I’m sure your supervisor will correct you or point you in the right direction if you go astray. As far as a job afterwards is concerned, academics are judged on their impact factor, which is often based on their publications. Some (industry R&D) places will use a PhD requirement to narrow down the candidate list and ensure the ability to understand complex problems and educate yourself.
In my field (Computing Science), I’ve seen some thesis where each chapter has been published as a paper: a review paper plus two or three experimental papers. I’ve seen another which resulted in a single journal paper covering most of the thesis, but if you spend years gathering a dataset, the major contribution is the dataset itself, not the publication that describes it (although that’s important, too). Some advice has been to view the thesis as a series of sprints rather than a marathon and "publish or perish".