It goes in cycles. The Old Nats had a bunch of knuckle-ballers in the late '30s, early 40's (have to look that up...Dutch Leonard is the only guy who comes to mind). In the late '50s, Hoyt Wilhelm was almost the only guy throwing the pitch. The disadvantages are all those mentioned above: Gus Trandos used a super-sized mitt to catch Wilhelm. Advantages as mentioned: you can't steal if you can't get on base.
Cycles and fads: Elroy Face was one of the few pitchers to throw a fork-ball, and went 19 -1 as a relief pitcher one year. (As best I remember, and I was about 12...). The close cousin of that pitch, the split-fingered fastball, became "everybody's" pitch after about '86, when a nothing-much pitcher for Houston tied the super-Mets in knots in the NLCS.
The knuckle-ball will be back.