Induction Motor Rotor Position and Speed Control
Induction motor does not have any magnets on the rotor. It has windings. You can drive induction motor by AC sourse without any controller.
BLDC motor has magnets on the rotor and it must be driven by electronic speed controllers. Generally, BLDC works with PWM signals.
As you said, the rotor position can easily measured by some sensors on BLDC. However, on induction motor case it is not necessary actually. If you want to use induction motor with varying speeds not constant,you can change the supplied frequency of AC power to reduce or increase the RPM of the induction motor.
I think it is just about usage areas and physical properties of these two motors.