Tesla Model S inverter DC bus voltage
The induction motor has fewer turns of heavier wire than normal .The power of the motor is the same .It is just more amps at less volts .Say if you consider higher DC  bus voltages  like Porshe the induction motor would have more turns of lower diameter wire.If the Bus DC voltage was really high   like thousands  then  insulation issues would kill the concept .If the DC bus volts was really low   like say 48 then the motor wire would be very thick and cable copper losses would be high unless you used very heavy copper.Sure you could use a boost converter like you said but at the power ratings needed it would cost some money   and  add some weight  and waste some power.