You see those automatic faucets at public restrooms for a few reasons. Usually it is quite annoying to have them, because normally they don’t have a good water pressure, the water is not of a correct temperature and it usually stops flowing before you are done washing your hands. Well what are the benefits then?
Biggest reasons for the public lavatories to have them, is the fact that they are hygienic. No-one is touching the faucet, so there is no problem of transmitting bacteria when you wash your hands. Normally you would use your hand to make the water flow, and after you would close the tap with the washed hands. You just used dirty hands to open the tap, and you are getting those germs in your hands again. A sensor faucet does not have this problem as it is controlled by a sensor that activates when you move your hands towards it.
Another big reason for automatic faucets to be used in public restrooms is the water saving that they provide. Normally people leave faucets open by accident or on purpose. This causes a lot of water to be wasted. With an automated faucet the duration of the water flow can be pre set, and this kind of behaviour can be prevented.
The reason for someone to dislike a faucet like this, is that they have only experienced them in public restrooms, where water saving is a major worry. If you would purchase an automatic faucet to your home, you could easily set it so that it provides you with a comfortable amount of water at the correct temperature.