There are two fundamental issues with the mobile first approach.<p>Duplicate effort does incur a real cost in terms of time to delivery. Duplication is a clear sign of inefficiency. A platform that provides native support for multiple platforms reduces such duplication.<p>The maintainance cost of providing multiple platform-specific implementations compounds over time. For every feature added there&#x27;s a chance that subtle differences will be introduced. In a perfect world one platform developer will have an equal level of skill and understanding as a developer for another platform. In practice, there&#x27;s no guarantees that both versions will be kept in sync. The differences and abstraction leaks become technical debt and accumulate as the platform grows&#x2F;changes over time.<p>Now, lets say you want to provide a web, iOS, Android, and Desktop interface for a platform. Would you choose to do 4 independent implementations in 4 different languages. Or 1 in a single language with platform-soecific differences?<p>Platform duplication is a violation of DRY at the system level and incurs the same problems of diplicating code, at a much larger scale.<p>The Russian Facebook is basically a independent fork. It&#x27;s not required to remain feature-complete and in sync with the official Facebook platform.