Another thing to remember is that many, if not most, PC buyers have a limited budget. Spending too high a proportion of this budget on the graphics card either compromises other parts of the build that may be more difficult to change in the future, or encourages people to spend more than they really should. It is always possible to spend a bit more here and a bit more there to get ever smaller increases in performance. In the end, perfection is never achievable. Good enough is good enough.