They usually turn out more reliable (if built right) because you can remove the transmission entirely, which is a major complicated piece of mechanical engineering that is prone to failure.
They also get to run the engine at a lower duty cycle while it is warming up, which is a big source of wear and tear for a gas engine. They also never have to run a rich mixture because the power gap is made up for by the electric motor.
They are more reliable because Toyota sells a large fraction of the hybrids. Non-Toyota hybrids are less reliable than both gasoline cars and EV's. Maybe that's circular because a large fraction of the non-Toyota hybrids are Stellantis...