Why - many large industrial sites use 3.3kV motors and so on.
The voltage isn't fixed at 230 (or 110) - that's just the most suitable for most end users taking into account the factors.
Like why we use 3 phase and not 7 phase and so on - it achieves the best balance given the technology we have
Right, but 3.3kv with EPR insulation, stress cones and OCPDs to achieve rapid disconnection. The added cost and complexity would outdo any copper savings of using 3.3kv in residential and commercial.
400 volts on the other hand uses PVC insulation and at 230 volts to ground can use standard MCBs.