With trackers, you're editing a series of events. Events can be notes, parameter changes, or commands such as "reverse this sample's playing direction now" or "move the playhead for this sample to exactly 50%". Those are common tasks when making electronic beats.

With pianorolls, everything has to be represented as a note or an automation curve. The examples I gave above become difficult to represent properly, and are often done with plugin-specific keyswitches or velocity switches. You end up with a D sharp that actually means "change to sample number 2", that kind of thing. I don't really see how it's better for working with audio clips.