Kinda like saying &quot;why is that muzzle loading soldier able to maintain constant fire for 3 hours when the guy holding the machine gun runs out in 10 minutes&quot;<p>The two main factors from my point of view are:
1) Modern phones are more capable and allow you to drain the battery faster.  (better radios, larger&#x2F;brighter screens, LED vs LCD, massively more powerful processors&#x2F;GPUs).  An iphone 5 has a standby battery life of ~9 days[0].
2) Cell phone manufactures target 10-24 hours of battery life when they design phones (smaller is better).  I&#x27;ve found that my e-reader runs out of battery more often than my phone.  Remembering to plug it in once every week or two is harder to do than getting in the habit of plugging in my phone every night.<p>[0] <a href="https:&#x2F;&#x2F;support.apple.com&#x2F;kb&#x2F;SP655?locale=en_US" rel="nofollow">https:&#x2F;&#x2F;support.apple.com&#x2F;kb&#x2F;SP655?locale=en_US</a>