With the brain's propensity for homeostasis, how can some drugs be labelled addictive and others not? The human body is always striving for homeostasis. One of the purposes of the brain is to maintain homeostasis, but also the brain needs to maintain homeostasis within itself.

Ergo:
Given the use of any drug, that acts of the brain, will cause a change in brain chemistry.

Why are some drugs are regarded as addictive and others are not?
Here is a part answer to your question.

According to the article Drug Facts: Understanding Drug Abuse and Addiction and Drugs, Brains, and Behavior: The Science of Addiction, addiction is a disease caused by some types of drugs.  Specifically, they rewire the brain to cause an overstimulus of the 'reward' centres and by imitating some of the pre-existing neurochemical messengers in the brain - essentially, 'tricking' the brain that homeostasis is maintained.

Related, the article "Why does the rapid delivery of drugs to
the brain promote addiction?" (Samaha and Robinson, 2005) concluded that the rate of delivery is an important factor:


  that rapidly
  delivered drugs might promote addiction by promoting
  forms of neurobehavioural plasticity that contribute to
  the compulsive pursuit of drugs.