Web abstraction layer for UI is too heavy and very limited. Even today we can't have multithreaded scrolling or manage painting with the latest web standards.
Native platforms don't have to worry about "other browsers" so they can optimize their UI abstraction layer specific to their target devices. They also don't have to wait for ever to get consensus for new APIs and architectures firm multiple parties that don't specially care about your platform.
No wonder native apps are so much better for the user and with recent developments in tooling they are as easy to work with as th eweb technologies