Some of them are. Some of them are truly pointless. Neal Stephenson apparently had a giant map of 18th century London on the wall of the room where he wrote it,

Some of them are. Some of them are truly pointless. Neal Stephenson apparently had a giant map of 18th century London on the wall of the room where he wrote it, and as such apparently feels compelled, on certain occasions when a character goes from one place to another, to name every street he passes on the way. That's not atmospheric or interesting, it's just filler.