The quick answer is MARKETING!
Why do drop shoppers promise the earth to their customers?
You have to remember that ebay makes money from sellers, the more sellers the better for ebay, the more sales per seller, the better for ebay.
It's in ebay's best interest to have its sellers striving for maximum sales, that's only going to make ebay more cash!
Offering them a reward (Power Seller) is their way of giving its sellers a target to strive for.
As I said, you already have to have been making good sales to even get to the point of being offered entry as a Power Seller, just because you reach that status doesn't mean that 1000 white doves will burst out of a paper cage and fly off towards the heavens.
The title itself means absolutely nothing!
If you make Power Seller, then stop what you had been doing to get you to that point the very next day, then your sales will drop......being a Power seller will mean absolutely nothing at all!
If your aim is to become a Power Seller, then your focus needs to be on what it will take to get to that level, will do you absolutely no good simply focusing on becoming a Power Seller itself.