If the data stored on the NAS were streamed in real time, and there was no error checking taking place then I might agree with you.

Fortunately the data is not streamed in real time - it is transmitted in packets, and those packets are not necessarily transmitted in exactly the right order.
As long as the packet arrives into the playback device's buffer within a certain time window the data is sorted into the correct order for playback.

If the data arrives in buffer outside of the time window then the result on the playback is catastrophic - the playback stops.

While all this packet data is being transmitted it is also being error checked, and again if an error check cannot be verified the whole thing grinds to a halt.
So when things aren't working properly you know because you get silence when there shouldn't be any.

Of course it's your right to completely ignore common sense and believe what you want with regard to networked music players.
If you want to believe that all the networked bits contribute significantly to sound quality you should be beating on the door of your local Naim dealership down and begging them to rape your wallet or credit card.