The main problem with pretty graphics is that you actually lose out on the kind of variety a more abstract graphics style would allow, e.g. by distinguishing objects in a textual description you can have millions of distinct objects (e.g. in something like Dwarf Fortress with its item and character descriptions), much more than you could if you had to represent everything graphically.
I suspect the prettiness sells better in the investment meetings to people who have no clue about gameplay anyway.