Why do opposite charges attract and like charges repel?

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The discussion explains that the outward pointing electric force vectors around a positive charge and inward pointing vectors around a negative charge are based on conventions. It establishes that positive and negative charges are defined as such for clarity in understanding electric forces. The test charge used to determine the electric field is conventionally taken to be positive, leading to the principle that like charges repel and opposite charges attract. The field lines are thus directed away from positive charges and towards negative charges. This clarification highlights the distinction between electric force and electric field in the context of charge interactions.
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Why does the electric force vectors around a positive charge point outwards and the electric force vectors around a negative charge point inwards?
 
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Those are just conventions. At first we take the convention that the two kinds of charges observed in the nature, be taken to be positive and negative. Then we take the convention that the test charge that is used for determining the electric field be positive and because likes should repel and unlikes should attract, the field lines should go away from positives and to negatives.
 
the field lines should go away from positives and to negatives.

You certainly mean the force, not the electric field.
 

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