|Indeed. But the problem can be finding the file if you don't know when it was backed up.|
Say I have a file called something.txt and I accidently delete it. Now I know it was there yesterday, but it might not have changed for months. So I have to go back to the last full backup. On a home system you probably don't do full backups more than once a month, because they take a lot of time.
So you go back to the last full backup. But wait; what if you changed it since then? How do you find the latest copy other than looking at all the incrementals too. And it's actually worse than that. Those full backups take a lot of storage, so you're going to have to delete them after a while. How many do you keep? A year's worth? What if you want a file you deleted more than a year ago.
Time Machine (and Genie Timeline) makes this easy. You know the file was there yesterday, so just open yesterday's view of the file system and there it is. And you can keep files that seldom change for longer; because you're only taking incremental backups, which build on the first full one, it needs far less space than multiple full backups that each contain identical copies of seldom-changing files.
Once you've used a contnuous incremental system like TM you won't go back to the old way of doing things. The good news is that they are going to build this sort of thing into Windows 8.