Shredder?

Today's question is:  Why do people do annoying things on the commuter train?

Background:  I'm sure there are at least a hundred stories I could list here and maybe for the next few days I'll post a couple of my favorites.

Years back, before I had children, I used to use the commuter rail to get back and forth from work.  Our rail line, the Metra, is pretty nice for a commuter rail.  I found the ride to be relaxing, well, most of the time anyway.  

If you don't know, there is a certain etiquette on the train.  

Seriously, talking with other patrons is discouraged, especially in the morning (well loud talking that is).  If you sit on the top, you aren't supposed to put your feet on the ledge, because you might drip onto people below.   Cell phone conversations are usually looked at with a raised brow (nothing like knowing the guy's story sitting next to you because he wasn't smart enough to be discreet).  And paper shredding by hand, strictly forbidden.  Not really but it should be.

One morning, as I was traveling to work on the train, I was all ready to relax on my way into work.  The second I sat down, on the upper deck, the only place I like to sit, I heard a noise.  Oh my goodness, there was a lady sitting across the train from me shredding a huge ass small stack of papers, by hand.  The sound was so annoying I thought I was going to lose my mind.  I kept an eye on her so I could calculate when my misery would be over.  At last, she was on the last piece and I was about ready to do a happy dance and enjoy the last few minutes of my ride into the city.  It was then that I noticed that lady reaching into her bag to pull out more paper.  God help me.

Why don't people think?