It would be abnormal under almost any system for the dissertation advisor not to read a student's dissertation. However, how closely and in how much of a timely fashion the reading is done will depend on the circumstances and the individuals involved.
In some educational systems, the supervisor is part of the faculty committee that reviews and evaluates the dissertation. Under such a system, it is basically mandatory that the advisor read the document, since they are supposed to judge its quality. Normally, the advisor does not wait for the final version to do this; rather, they read earlier drafts, and only once the advisor is reasonably satisfied with the quality of the dissertation is the near-final version passed on to other members of the examining committee, so that an oral defense can be scheduled.
In other systems, the student's advisor is explicitly not part of the group that evaluates the dissertation. In this case, it is conceivable that the advisor may take a very "hands-off" approach to the production of the actual written document, leaving that basically to the student. Whether this is a reasonable attitude for the advisor to take depends to a large extent on whether final approval is really a rubber stamp. If there is a real possibility that the student may not pass, then the advisor should absolutely take steps to assist the student in getting their dissertation into an acceptable form.
Personally, I feel that whatever the system, the advisor should be fully available to assist the student, if the student makes it clear that they want help. However, some advisors, under some systems do not feel the same way. That's unfortunate, but at the dissertation writing stage, it's too late to switch to a more cooperative advisor.