Please explain what I'm doing wrong.
Nothing, and yes you need Impulse to restore them. Note also that you are backing up the programs as they are installed on your machine. If you want clean backups, open Impulse, shift-right click on a program's icon, and select "download and archive" from the right-click menu. These will also be impulse files requiring Impulse to restore them.
Note also that either of these methods are o/s specific backups. In other words, if you have xp installed now and backup, then switch to Win7, your backups aren't any good (at least for some programs, not sure about all).
You can login to Impulse Anywhere here to get clean downloads which are not o/s dependent:
I don't think those include beta's, I think it's only the last non-beta releases. Also, there are 2 files for some or all of the programs, an .exe and an .impulse data file. I've never actually tried to install one of these, I'm not sure if the .impulse file feeds the .exe or if you're right back to needing Impulse. I would imagine you would at least need Impulse installed to phone home, but not sure.
Have fun Dave.
[sheesh - way slow as usual ]