Why design for mobile?

Nearly a year ago now, Pew Research Centre’s Internet & American Life Project found that cell phone ownership among adults in the US had exceeded 90%. As of Jan 2014, 58% had smart phones.
In Asian countries, the percentage generally exceeds total saturation due to multiple handsets.
For growing nations, such as India who have a mobile ownership of 15% at the end of 2013, are seeing massive growth with numbers of handsets set to boom.

What does this mean for mobile design? With the android market booming as costs reduce, the interface of our handsets become a more vivid and diverse location. As of the last quarter of 2013, the android market sat at triple the size of IOS. The IOS market however has also grown, lending towards a sign of overall prosperity for the medium.

What can be understood from this is that the future of digital design will need a firm grasp on compatibility with multiple handsets and multiple cultures.