Tandem Rotors vs Conventional Systems for Helicopters

Hello everybody,
this is my first thread in this forum.

I have been wondering for which reasons the tandem rotor system for helicopters, like in Boeing Vertol models,
hasn´t had a wider use in the industry.
If I´m not wrong, the tandem rotor system makes use of all the available power for lift and thrust whereas, in the conventional
system, part of the engine power is needed to drive the antitorque rotor, which produces no lift.
So, the tandem rotor seems to have a clear advantage.
But why hasn´t it had further applications than the CH-46, CH-47 and few other models (Bristol Belvedere, H-21, a Yak model and few others)
Does it have some major drawback compared to conventional systems?
Is it there a BoeingVertol patent that prevent others from building helicopters with tandem rotors?

Thank you

Stefano