Question on hybrid vehicles

I don’t know if this topic has been discussed here somewhere, but I have been wondering a few things about the hybrid vehicles for some time now. Why are there only hybrid vehicles that switch from a certain speed / xx km to pure combustion engines or stop those where the electric motor only “supports” the combustion engine? With locomotives and ships the diesel-electric drive is quite common. r permanently on a generator, which supplies the current for the driving motors. – no heavy batteries need to be installed – the problem of charging is eliminated – the power characteristics and the torque of the electric motor can be used fully