You'd use this if the stored fix parameters were invalid. Moving 500km since the last fix, or if the internal clock was wrong, or if it had been a long time since your last fix. The idea is that you are offering your GPS some hints about where to start looking.
If you can give a reasonable hint to what time it is, the receiver will get code lock much sooner than if it has to do a cold start - it knows what code words it should be looking for.
If you can give it an initial position, that helps to bootstrap the navigation solution, and also helps with initial acquisition by limiting the satellites sought to the ones that could actually be visible from your location.
By allowing you to force the ephemeris and almanac to be cleared, you can prevent the receiver from using stale data. After 3 or 4 hours, your ephemeris should still be valid, but your clock might have drifted; you'd be doing either a hot or a warm start. Probably under 10 seconds for a hot start if you have good skyview.
Have you tried testing the effects of sending good data (ie. the last good fix) as well as sending bad data (like time in the past/future or a postion on the other side of the world?) I think you would find that very educational.