I'm currently a PhD candidate, and our program includes separate written and oral qualifying exams during the first year or two, and a public defense of the dissertation at the end. I thought some minor variation of this was nearly universal.
It's also my observation, by the way, that the public dissertation defense (and even the written dissertation itself) is less of a big deal than outsiders tend to think. What matters is doing the research that the advisor / committee wants, and working on some number of papers that get accepted into workshops / conferences / journals (depending on the field). Everything else seems to be kind of a check-the-box formality. By the time the committee agrees that someone has done enough to defend, it's pretty much a done deal.
My particular school and department is interesting because it doesn't have any hard requirement for publications, and it aims to have students finish a PhD in about three years of full-time work (assuming one enters the program with a relevant master's degree already in-hand). There has been some tension between the younger assistant professors (who are still fighting for tenure) and the older full professors (who got tenure in, say, the 1990s). In practice, the assistant professors expect to see their students publish (with the professors as co-authors, of course) and would strongly prefer to see a dissertation comprised of three papers stapled together, regardless of the what the school and department officially says. The full professors, on the other hand, seem to prefer something more like a monograph that is of "publishable" quality, maybe to be submitted somewhere after graduation. They argue that the assistant professors should be able to judge quality work for themselves instead of outsourcing it to anonymous reviewers. Clearly, there are different incentives at play.