In simple terms, the more elements added to an antenna increases its "focus" for more signal strength or 'gain' ... so if you have a weak channel and your TV requires a stronger signal, that is one way to achieve it. Narrow-beam reception, something like a pinpoint driving light on a rally car.
On the other hand, the more elements added to an antenna reduces its ability to receive a variety of channels that are transmitting from different but nearby sites, such as on adjacent mountain tops. (both sides of the road)
So, in some situations a wide-beam rally-car foglight (fewer antenna elements) is a better antenna choice.