Noise, by definition, doesn't have a qualifying characteristic. It just means "all signals we're not interested in". That means your ability to filter out noise is strongly dependent on having pre-existing knowledge about the shape of the signal you're interested in.
Self-clocking signals are useful when the ambient noise level is low with respect to the signal, but if your signal is just "these two droplets in an ocean" you will not be able to filter out enough of the signal to detect the edges of the original signal.
Having a very reliable clock frequency means you can apply a very exact filter to lock on to the signal you want, thereby making the transmission less sensitive to interference from other radio signals. Just having a sensitive receiver isn't enough, because a sensitive receiver will also pick up more of the other radio signals.
Self-clocking signals are useful when the ambient noise level is low with respect to the signal, but if your signal is just "these two droplets in an ocean" you will not be able to filter out enough of the signal to detect the edges of the original signal.
Having a very reliable clock frequency means you can apply a very exact filter to lock on to the signal you want, thereby making the transmission less sensitive to interference from other radio signals. Just having a sensitive receiver isn't enough, because a sensitive receiver will also pick up more of the other radio signals.