why does "random" never work the way I want?

So I added a bunch of stuff to my "On The Go" playlist on my iPod. There were a couple songs I wanted to hear more often, so I put more copies on the playlist. I always run my playlists on random, so I figured those would just pop up more frequently.

Instead, I got "Eyes of a Stranger" three times in a row and "Supermassive Black Hole" twice in a row.