Yes and no. An antenna tuner primarily matches the impedance of the antenna to the radio, allowing maximum signal transfer. It's very important when transmitting, especially since modern solid state radios often dislike high SWR. For receiving, I am not convinced of the benefits personally, except in some cases.
I have improved reception on longwave with a tuner, I believe this was a case where the impedance mismatch was really horrible. It was a homebrew affair, two variable caps and a tapped inductor.
Another use is to reduce images and overloading from nearby AM transmitters, although I don't have any experience with this.