It's more that all the optimizations and strategies which apply to a browser built to hold many open tabs at once, support many standards and protocols and quir

It's more that all the optimizations and strategies which apply to a browser built to hold many open tabs at once, support many standards and protocols and quirks etc. must be loaded into memory for a simple application that is not a browser. You get all the tradeoffs of Chrome (e.g. cache everything you come by) outside of Chrome proper.