I think that's an HTC customization. On my HTC Touch Pro II I also don't have the time options for repeating an alarm but I do on my TyTn II. Both are running WM6.1. I think that in Windows Mobile builds after a certain date HTC just doesn't include the options.
It takes all the running you can do to stay in one place.If you want to get somewhere else,you must try to run at least twice as fast as that.