If winlogon runs in the same security context and the same desktop as explorer.exe then a key logger will be able to intercept all logins, and a screenshotter will be able to take screenshots of your login screen. Clearly you don't want that to be possible.
Or are you saying that they never should have made Ctrl-Alt-Del do anything else but starting the task manager?
Or are you saying that they never should have made Ctrl-Alt-Del do anything else but starting the task manager?