The ability to render things client side in a way the server doesn't anticipate, e.g. native widgets on various platforms. I don't see myself loosing anything

The ability to render things client side in a way the server doesn't anticipate, e.g. native widgets on various platforms. I don't see myself loosing anything of value? If the data you are talking about is e.g scroll back, nothing is preventing me from storing a wee bit extra metadata on the server.