What one forgets to observe in this powerplay rule is, "It is mandatory only in the first 10 overs" and next two set of 5 overs is at captain's discretion.
Imagine a situation, more often than not in subcontinents, where in the batsmen score 70-80 runs in the first 10 overs. Do the bowlers have to go thru the next five overs like that. That would definitely boost the batting teams score. By defering the powerplay to a later stage might even reduce the final score.
You people forget to see this because the captains of both sides used it in first 20 overs. As well, the scoring rates weren't high at that time.
