The article left out survey data...
Be sure to check out the unaltered "Demographic differences in iPhone and Android Ownership" table from the survey link. This report suspiciously leaves out age and gender data from the infographic.
That data illustrates that Android is more popular with age groups 18-24, 25-34, 35-44, and 45-54, while iOS is more popular with age groups 55-64, and 65+. Android is also notably more popular with men, while iOS and Android are split between women.
The survey would have been more meaningful if they controlled educational attainment percentages based on income bracket. Otherwise income is just a confounding factor.