You could start a 79 cc without a centrifugal or manual clutch and take off if you push it a bit to get going.
But when you come to a stop or slow down below idle speed your motor will stall and you will have restart it.
Not too many people will put up with that.
I have ridden a clutchless friction drive like that. Everytime you stop the motor stalls so you have to pedal to restart.
A pull started motor would be harder to use because if you are stationary the motor would try to move the
bike then die when started.