Although not always the case, but some people buy bikes at garage sales for a screaming deal and not realize what they got. My non-biking friend had bought a Bontrager at a garage sale for $10 thinking it was just a department store bike. She wanted a bike for school. When I told her that it's worth way more than what she paid, she got a better lock but she still uses it for school and locks it wherever it's convenient for her. As for the seller, my friend said the garage sale was due to a divorce so we figured the seller didn't know the bike's worth either.

giantcfrl, I know what you mean about bikes being safe where you live. When I was in Tokyo, I was amazed by how most people left their beaters unlocked! They just shove it between two other bikes and leave it. What really surprised me was that later in the evenings as people retrieved their bikes to continue home, sometimes there would be a lone bike left standing by itself a few meters away from several other bikes which are also unlocked. Sometimes, I saw a station attendant move the bikes closer together just to free the sidewalk of the bike clutter.