I really don't understand your logic. Please, look at the price chart. The price is falling down.

Why do they sell? Because they don't believe that Steem will rise in price or they just want quick money. That's the whole kitchen.

If someone only sees the price, they are missing the whole point. If the price over the next year goes down 50% and my coins go up 80%, have I gained, or lost?

I have gained.

Yes, I'd like the price to rise or be stable, but I have the understanding that the coins we are being given as SP-holders to counter inflation aren't handed out for fun. They are done because it is understood in the design that we will be losing value.

Imagine the scenario where you have 1000 SP and in a year you have 2000SP. Price stable at 0.0025. So now instead of 0.0025 x 1000 = 2.5btc, you have 5 btc.

You cannot really make a steem-price comparison or apply classic analysis on motives when factors like these are in play.