"We want to focus our efforts on the mobile platforms the vast majority of people use," WhatsApp said in a blog post.

WhatsApp's decision makes sense if you look at the changing landscape of smartphone operating systems. As this chart from Statista shows, the smartphone market is dominated by Google's Android and Apple's iOS, each accounting for 81.6% and 15.9%, respectively.

That's a complete reversal from 2009, when smartphones were just starting to emerge: almost 80% of smartphones sold at the time had operating systems offered by non-iOS and Android players, like Blackberry and Nokia. Today, 99.5% of the smartphones run on operating systems offered by Google, Apple and Microsoft, according to WhatsApp.