In regards to the OP's original question about the usefulness of flashlights, I think I can shed some light on the issue (get it?).
My M9A1 has a rail and a TLR-1 attached to it. It is fun and admittadly useful on my pathetically lit local range but I will concede that during a home invasion at night the light would give away your position but there are benifits.
The first of which is simply having a light, but the real advantage comes from the distraction and disorientation that the light causes. I found this out by accident but try shining any kind of tactical light into a mirror, it is blinding even in a fully lighted room. Now my TLR-1 also has a strobe mode that I also tried in the mirror and my eyes actually hurt for few minutes after looking into the mirror for only a second or two. Obvious as it sounds, just because you have a light does not mean you have to turn it on, so don't rule out the possibility of sneaking around until you find something suspicious and then shining the light right into its eyes.
Now consider this from the side of a home invader. Even if he was able to shoot back it would be at best blind fire, while you would be able to line up a good shot.
My take is that, no its not necessary, but it is useful to have as an option.