According to this article, only about 1% of all humans are ambidextrous:
About 90 percent of people are right-handed, says Corballis. The remaining 10 percent are either left-handed or some degree of ambidextrous, though people with "true" ambidexterity—i.e., no dominant hand at all—only make up about 1 percent of the population.
Less dominance is observed in other animals, as indicated by this article:
Bill Hopkins, at the Yerkes Regional Primate Research Center in Atlanta, USA, has made even more contentious claims in recent years, asserting that his captive chimpanzees exhibit a 70% right-handed preference for many tasks requiring manual dexterity, a rate that rises to almost 98% for very specific tasks, like the precise over-arm throwing of objects. However, for everyday food-related tasks (like cracking nuts or digging out honey), the rate remains closer to 50-50.
I am wondering if there is any theory that explains why ambidextrous persons are so rare. As a totally layman when it comes to biology it seems that this would require a more complex brain to wire all the complexity to both members and this would be rarely justified (virtually all tasks can be done without being fully ambidextrous).
Question: Why are ambidextrous persons so rare?