Pointless to me, except maybe in a true emergency situation to keep signaling while I slept or something like that. Otherwise it's just annoying. I avoid any light that has it in the main mode sequence, i.e. hi>lo>sos. If it's hidden like in a Quark Tactical UI then hey why not have it in there.
Edit: Actually, I can now think of no reason to have SOS, even on my Quark lol. It has the beacon modes, which would conserve more power while still signaling at full brightness.