Seems like a fly rod from a boat could cover more water, deliver more time during which your small bait is in the prime strike zone.  Of course, would work best during those few times when bass are chasing/stalking small fry or polly wogs or baby frogs up into shallow water/grass. 

 

What I mean - while drifting down the bank, paralleling the bank, you don't have to reel all the way back in and re-cast, too often miss casting, landing short or long or too hard.  With the fly rod your distance is set, the line is out, you back cast and then settle your light bait onto exactly the next spot on the forecast.  The bait is sized to the forage and has a new/different look too.  Then hand retrieve through the prime water, and recast, again just right, without having to rewind line, to the next spot.  Efficient.

 

What am I missing?

Only that you can throw wet flies, streamers etc. too. You can fly fish the whole water column if you want to. Probably not the most efficient deep water method but possible.