I began jig tying, after a very long fly tying hiatus, so that I could tie float-n-fly jigs expressly for smallmouth bass fishing. It's really just a very old crappie fishing technique in my opinion. This "renewed" technique has been marketed toward smallmouth and spotted bass fishermen because, as a winter time technique, few other methods work nearly as well. I like to use it on a local river during winter when few others are fishing. Have caught a good number of smallmouth bass with a few large ones in the mix.
Plus, a myriad of jig styles work. Often, the patterns can be quite pretty and very fun to tie.
The swivel system with center-weighted bobber might be fine for lakes, but it's unnecessary for river fishing in my opinion. Personally, I don't worry about lift bites. So, I find that a weighted-orange Comal float fixed to my main line at 3-5' above my jig does just fine.
I posted some tidbits about this topic at the link below a while back.
LINK