I have been observing bicyclists of all ages riding against traffic my entire life. Sadly the schools tell children to walk against traffic which is a good idea and so the child thinks that this applies to riding their bicycle. Sadly even when 40 years latter as an adult they start to again ride a bicycle they often repeat the same dangerous behavior.
In the 1970's when city and state engineers started to paint lines for bike lanes they often put riders in situations where they would be going against the flow of traffic or past freeway off-ramps where motorist would not be expecting them. Unfortunately engineers are no better today then they were 50 years ago. Something about engineers that keeps them from being able to learn as they age.