Yes, an alternative motive but an honest one. Because I'm leading my visitors through not just the first page or 3 pages but as many as possible. You need to know that when someone first comes to your site they need 3 things which is where they should start, where to go and how to get back to where they were. The purpose of my menu bar is that no matter where you are on my site, if you've seen something about what you've read and want to go back to it and find out more you can find it on the menu bar without having to go through this long page of retoric. Another way NOT to lose your visitors is cut out all that javascript and java junk.
Frames are really really really annoying also.
After that you have to paddle back for the next wave. Yes we all have bookmarks available and you probably have more bookmarks than you care to handle. You'll hear this time and again from me but time is money and valuable. Finding you again in a bookmark may not worth the time for many. Another way to keep your visitor on your site is keep it EZ to load.