They aren’t very reliable because they run at the ragged limits. It is a competition, after all. Motorsport has always been like that, nothing to do with current PU tech.
The reason we don’t use them in regular cars is because it’s expensive to make, and combustion engines are being phased out anyway.
And the only reason they are so efficient is because they run them at the limits.
No, running engines at the limits makes things less efficient, which is why on fuel-limited tracks you see a lot of lift and coast and turning down engine modes when that was a thing.
The efficiency comes from having two different complex energy recovery systems, which is what makes them expensive to transfer to the road.
Still, you’d see more real world applications if countries’ carbon regulations were tighter.
