I proved the brand I bought works, by leaving it outside the house in a dark place which I knew had mosquitoes. I scored a dozen before the rechargeable battery ran flat, which takes about 4-5 hours. Presumably the device is intended for indoor use, while one is sleeping. In a house with insect screens, that is only the odd mosquito. The instructions do say it works much better with no other light sources.
Your comment simply demonstrates you have a closed mind.