Because in the windows market, surface isn't a laptop targeting video editors, game programmers, etc. It's a thin and light entry. Contrast with lenovo portable workstations which got 64gb over a year ago: http://www.theverge.com/2015/8/11/9129681/lenovo-skylake-xeo...

Apple produces every osx compatible device. This means it needs to produce at least one device that can meet the needs of power users.