Tramadol, like several other opioid drugs, e.g., hydrocodone and oxycodone, has been increasingly associated with dependence in recent years, so have been rescheduled to a more highly controlled classification by the DEA/FDA.

This is not a new phenomenon. Many opioids, including heroin, when introduced where thought to be "less addicting" than older opium-derived drugs. Of course, this turned out to be mistaken and now it's being played out with several "less addictive" opioids in common use.

I certainly wouldn't regard tramadol as innocuous, besides abuse and dependence, it can also have serious interactions with other medications, particularly serotonin overload which can be deadly.