Many, if not most, abusive relationships escalate over time as well. (Frog in the pot) As the victim gains more tolerance, loses self esteem, and trauma bonds to the abuser, the look of the abuse changes.

Mean jokes and put downs turn into hurtful comments and insults, and eventually can become overt verbal and emotional abuse. Some abusers begin to covertly physically abuse their victim- "accidentally" knocking them down or slamming a door into them, and that can eventually give way to full blown overt physical abuse in time. They test to see just how far they can take the power trip.

Even with a family history of neglect and/or abuse, relationships don't generally start out looking like they are bad. For some people it's a process where you wake up one day and think "how the hell did I end up here?"