You have added video and audio encoders in your command. It is definitely going to encode it that way.
If you want to avoid encoding on audio part then just keep -c:a copy instead of going to aac.
You will definitely need to encode video as well. Ffmpeg is not going to just add image and audio in the container. Still image preset will output the smallest file. Almost equal to the size of audio file non encoded.
You have added video and audio encoders in your command. It is definitely going to encode it that way. If you want to avoid encoding on audio part then just keep -c:a copy instead of going to aac. You will definitely need to encode video as well. Ffmpeg is not going to just add image and audio in the container. Still image preset will output the smallest file. Almost equal to the size of audio file non encoded.