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You probably don't pay much attention to DH racing, nor Freeriding for that matter. Most DH'ers and Freeriders that I know use platforms. Have you researched it that much?

Your question could be taken two ways. I don't know why you narrowed your statement down to DH because the OP wasn't even asking about that aspect of riding.

1. You are genuinely asking if clipless is necessary.
2. You think what you're doing is fine and anyone who doesn't use platforms like you do is rediculous.

Honestly, if I were to do DH racing where I'd occasionally drop a foot for cornering aggressively...I'd most likely ride platforms too.

For other types of riding, I'd probably stick with my SPD's. For the All Mountain riding that I do right now, I find that I am not afraid to corner aggressively w/o dropping my foot off my pedals.

I think it's a comfort zone thing. I'd like to be able to ride on flats the way I can ride on SPD's, but I can bunnyhop much higher with that added "cheater" plus I can pedal much more efficiently with clipless pedals. I can pull up with one leg as I push with the other. In really rough sections of trail when my bike is bouncing around...I don't accidentally lose my footing.

So in the case of the Captain...no. Actually if all you're doing is going downhill, pedals aren't necessary. Just sit down, hold your feet up, and hang on. But don't forget other scopes of riding.