Final answer:
Most objects have nearly equal numbers of positive and negative charges because of the law of conservation of charge, resulting in these objects being electrically neutral and not usually exhibiting static electricity.
Step-by-step explanation:
The reason why most objects tend to contain nearly equal numbers of positive and negative charges is due to the law of conservation of charge, which states that electric charge can neither be created nor destroyed. When an object gains or loses charge, it does so in equal amounts of positive and negative charges to remain neutral. This is why objects don't normally exhibit static electricity. Materials can be charged in various ways such as by contact, conduction, and induction, but it results in the separation of already existing charges rather than the creation of new charges. Therefore, most objects around us are electrically neutral because they have balanced amounts of positive and negative charges.