Usually FE and BE are developed by different people or even teams. It's helpful to decouple release cycles of both components, or else a bug on one component could block deployment of a different component. It's important not to decouple deployments of two components when doing so would save up significant resources, but here decoupling could be achieved by deploying a separate nginx server with static files – this is incredibly cheap, as there is very little static overhead, and performance is comparable.