In my opinion, yes, it’s very useful. You can be much faster and smoother (which also requires practice, of course). I wouldn’t limit it to the classical guitar world. I use this kind of “alternate picking” fingerstyle on a steel string acoustic all the time. (A good example is this recording of Is There Anybody Out There? – that’s the thumb holding down the bass and alternate fingers (mostly i and m) doing the other single note stuff.)
Note that I’m not saying you always use it. There are songs or passages within songs where something else makes more sense and/or is more efficient. But it’s the long-standing default approach in the classical world because it works very well. For me, it’s the way to go.