RV AC is all metal lines soldered, no flexing parts or seals or readlily/easily replaceable parts that hold refrigerant.
Automobile AC, every single part that holds refrigerant is replaceable and therefore must have a connection joint with an oring. It also has flexible hoses from compressor attached to the engine that move with the engine, those hoses mount to the vehicle body/engine compartment under the hood that is stationary. Hoses fail or leak all the time. Its usually that or compressor seal as the most common items. Just replaced a main manifold hose set on my 99 Tahoe last month, had a hole in it from flex/age/pressure.