Mosquitoes buzz in people's ears primarily because of the beating of their wings. The rapid wing beats create the buzzing sound, which is a byproduct of their flight. Mosquitoes are attracted to humans by the carbon dioxide we exhale and the heat our bodies emit, which leads them to fly near our heads and ears. Additionally, the buzzing may serve as a form of communication among mosquitoes, especially for mating purposes. The ears being close to the nose and mouth makes the buzzing sound more noticeable there as mosquitoes search for a blood meal. The buzzing is not meant to annoy but is simply the sound mosquitoes produce while flying nearby and seeking blood.

There is also a cultural explanation from an African folktale retold in the picture book "Why Mosquitoes Buzz in People's Ears," where the mosquito's buzzing is linked to a story about how its annoying behavior caused a chain of events in the forest, leading to the buzzing being a constant reminder of the mosquito's troublemaking nature.

In summary, mosquitoes buzz in people's ears mainly due to the sound their wings produce when flying near the head, attracted by carbon dioxide and body heat, combined with the proximity of the ears to these cues.