Well, my Linux-fu isn't very up-to-date, but my guess (which actually goes for any file system) is that a directory is a bit more than just a logical organizati

Well, my Linux-fu isn't very up-to-date, but my guess (which actually goes for any file system) is that a directory is a bit more than just a logical organization. It's an actual "thing" in your hard drive which keeps track of everything beneath it. And so it grows in size when more files are there, which slow down access.