Mosquitoes are nasty creatures. They bite; they transmit terrible diseases to people and pets; and from what I read, they have no redeeming value in the ecosystem.
Malaria infected some 212 million people worldwide in 2016 and killed an estimated 429,000. Mosquitoes spread yellow fever, dengue fever, Japanese encephalitis, Rift Valley fever, Chikungunya virus, and West Nile virus.