For the value for Steam, SCO is quite correct, the walled garden it is. What's more, if you ever look at the big box store ads during special sales, you'll find very similar style discounts - including doorbusters - under the exact same sales philosophy.
For the dev, the issue is much more complex. If you never haunted the discount bin at your local games shop, or went to a dollar sale at a big box store back in the day, you might think Steam a strange and unique place. But it's not. The idea behind an item like a game is to gather as much profit as possible. However, that does not mean sticking the price up at maximum forever. While that might seem best on face value, the number of people willing to pay top dollar is always low for common entertainment, and thus your number of sales will remain pitiful. You still want those top dollar sales, yes, but you can't leave the price up there forever. So, you leave it up there until you have exhausted all potential top dollar sales, and then ratchet down a monetary notch during a sale to gather a little more interest. Then go back up. Because not only does word of mouth often carry a few more item sales after a sale, the sale got people thinking about a game again. Back when the game was first released, they may have thought, hey that looks kind of interesting, maybe I'll get in on sale. But then they forgot about it. The sale got it back in their minds again, and though they didn't buy it during the sale, it's there now, which is a nagging possibility for a full price sale.
And then later, after you've exhausted all of the common sale notches, that's when you let your stuff go for bottom dollar, briefly. That kind of sale is the fastest way to get mass sales from people who will drop a couple bucks just to experiment. And maybe some of those will like your game, and so become converts, and be ready and waiting to buy your next release at full price. Plus those converts may even spread the word on places like the Codex, and so garner you a few more full price sales after the sale by word of mouth. Which is why, sales of a product usually increase both during a deep discount and for a while after it's over.
Trouble for a lot of indies is, though, they're so desperate for funds that they drop to deep discount soon after release, skipping the ratchet sales, because they're so desperate for funds and notice that they can't wait and try to build an audience the normal way. Vogel doesn't have that issue, though. He already has an audience.