Here's why:
* Dishonesty: Stealing involves deception and a violation of trust.
* Illegality: Stealing is a crime that can result in legal consequences.
* Harm: Stealing often causes financial or emotional harm to the victim.
While there are some figurative uses of "steal" that might not be inherently negative (like "steal a glance" or "steal a moment"), the word's core meaning is undeniably negative.