Why do I need to save them?

This thankfully doesn't happen often, but all applications can, and do crash... Safari is no exception. Imagine losing all those tabs you have open for research. Not to mention all the resources consumed with multiple tabs open. You backup your computer often, (well.. you should be) and now you can easily do the same with your browser tabs using SessionRestore. Who needs clumsy bookmarks - Go one step further, and save groups of tabs for instant retrieval anytime.