A list is a list, and saying so changes what readers get

Three related things marked as three related things behave differently from three lines that happen to sit together.

When you mark something as a list, you are telling every reader three facts at once: that these items belong to a single group, that there is a specific number of them, and where the group begins and ends. Those facts are useful to a person who can see them, because markers and spacing appear automatically. They are far more useful to a person who cannot, because the software can announce that a list of six items is beginning, keep count as it goes, and allow the whole group to be skipped in one movement if it is not wanted. None of that is available if the items are just lines.

There is also a distinction inside the idea of a list that is worth learning early. Some lists have an order that matters, such as the steps of a process, where doing the fourth thing before the second would be wrong. Others are simply a set of things with no sequence implied, such as ingredients or features. And some lists are really pairs, a name and its description, repeated. Choosing the right kind conveys real information about the content. Choosing the wrong kind is not fatal, but it quietly misinforms, and it usually indicates that you were thinking about markers rather than meaning.

Navigation deserves a specific mention, because it is a list almost every time and is very often not written as one. A row of links across the top of a page is a group of related destinations with a countable size and a clear boundary. Saying so is the difference between a reader hearing that a navigation region with seven links has begun and a reader hearing seven unrelated links appear one after another with nothing to indicate that they are the same kind of thing or that the group has ended.