Smallies can eat and spit a fly so fast, that most bites go undetected, especially when fishing the pre-spawn. After I started using a strike indicator a few years ago, my hookup rate increased dramatically and nowadays I hardly fish without one.
I like placing the indicator right up against the flyline, and for the most part use a 12-foot 8-pound straight fluorocarbon leader. This set up is used with up stream presentations, either dead drifted or employing a with-the-current retrieve. The bite can be extremely subtle, so if that indicator so much as quiver I will set the hook.