Until you have classified how each Favourite became the public favourite (by a variable or combo of two) and then the strength of "gap" between the 2nd Fav. basically you will never know.

But to answer your question wagering bias does occur but not how your thinking.

Best tip
Start handicapping your fellow punter not the horses. In wagering there are only a few strong variables at play

Joe Public will play those types (per variable and gap strength) of favourites over and over the same way day in day out.