SSTO is a great idea that logically comes first before any "mega-lift" system. But there are size limits to consider. Eventually there will be a need for payloads massing thousands of tons (and potentially much, much more.) The expense of launching thousands (hundreds of thousands, millions) of light components and assembling them in orbit eventually outpaces the expense of an "elevator".
Eventually we will need to move the means of production off-world to rid ourselves of the entire issue of gravity.