Availability of material on other services
While much of the popular older material may be available on Netflix (Top Gear, post 2005 Doctor Who, Red Dwarf, Yes Minister) the BBC Store did offer some old but less popular and less available material - eg Goodies, and Play for Today type material.
It seems while the BBC has been encouraged to make its archives available, there isn't enough interest in them as a whole to make it feasible in online format.