/diy/ - Do It Yourself

When I flush a toilet, I hear the noise of the water pouring from the high fill valve into the water at the bottom of the cistern below (a.k.a. how toilets work). But flushing at night causes noise for about 2 minutes.
Would putting a tube or pipe from the high inlet valve down to the bottom of the cistern not be much quieter after flushing? Why isn't this the done thing?