JSF is simply a UI technology that you can choose to use or not. There is no mandate that you "must" use it.
Personally, I really like what JSF has to offer. I also like other Web technologies as well - such as the ones you mention. Its even possible to combine several Web technologies to certain degrees with JSF. For example DOJO can work very well with JSF.
What I recommend for people curious JSF, is to take it for a test ride and see if it fits your requirements. If not, feel free not to use it. :-)
Joined: Aug 31, 2006
To finish answering your questions:
Struts is obviously similar to Faces in that it is an overall J2EE Web dev framework which is centered on an MVC architecture, however Faces provides more technology for the UI with its UI component model.