Actually, you have read a lot of such reports and didn't know it, because of the way they're written to grab attention (free advertisement for the vendor making the report).
For example, remember the initial report that started the whole "iOS users are on the web more" meme? Yep, the
Chitika report last year.
Inside it was this key paragraph, which was totally ignored by reporters:
"While third-party and our own observations have pegged smartphone Web traffic share as a near-tie, Apple has a decided advantage in the tablet market, where its iPad is unquestionably the hottest seller in the sector. This advantage is the largest contributing factor to Apples lead over Android."
Even when comparing the iPad to
just the iPhone, the iPad can make the iPhone's web usage look poor.
"...the proportion of iPad and iPhone usage can vary dramatically. The Hollywood Reporter gets 41% of its monthly US iOS traffic from iPad devices, Time is even more iPad-heavy with 70% of its US mobile web users preferring the iPad experience and Dailymotion sees an incredible 78% of its iOS mobile Web users accessing the site from iPads."