If we ever come to the point where all you need to develop a web browser is a wasm vm, don't you find exciting how much simpler a web browser would become? At the moment it is one of the most complex pieces of software out there. It is so hard to build a modern web browser from scratch nowadays that doing so as a hobby would take a lifetime. This takes the power away from individual developers, since it's not very realistic to build a new browser unless you are a big corporation with money to spare.
This situation also poses a big problem for the development of new operating systems. If your shiny, awesome, new research open source OS does not have a modern web browser, it will never reach wide adoption and thus never atract enough developers to build critical mass. The alternative is to make your OS compatible with POSIX and thus reuse the work of others so that you can build existing web browsers. But then you are most likely bound to become just another unix/linux alike, thus hindering innovation.