It&#x27;s simple economics.<p>If you have a lottery with a single 25BTC prize, that can only be played by spending electricity to compute hashes, then expect 25BTC worth of cheap electricity to be spent (every 10 minutes that the lottery is held).<p>The increase to 1 exahash&#x2F;sec is simply due to the latest generation ASICs having achieved 0.06 joules per gigahash.<p>At least this &quot;waste&quot; is reduced in half every 4 years.