This kind of thing became a hot topic at my current airline a few years ago, and we had issues with it at my prior airline as well.
@luvflyin quoted 91.131, but for us there's also Ops Spec C077, that among other things talks about the manner in which we're supposed to execute visual approaches, and one of the requirements that was consistently being ignored is that once we're in the Bravo, we need to remain there.
As an example of how we've been boning this up, I'll give you the one my company is constantly giving us crap about - the ILS to 12 in MIA. Here's the chart:
http://155.178.201.160/d-tpp/1809/00257IL12.PDF
If you're coming from the northeast, you'll end up on what's essentially a left downwind for 12. It's not uncommon for ATC to turn guys onto a base leg somewhere outside of PIANA (10.8 DME), and they'll be descending to 3000' at that point. They'll get the airport in sight and be cleared for the visual to 12. Since the pilots are hungry and there are a couple of pretty good Cuban joints in the terminal, the guy flying points the plane at VEPCO (or if he's *really* hungry, well inside it), notes that glideslope intercept at VEPCO is 2000' and starts bombing down to that altitude. Why in such a hurry to get down? Because the guy flying is thinking of sweet plantains and that cute Cuban chick at the register, so he wants to keep his speed up, and it's easier to dump a bunch of energy at the last minute from level flight, not a constant descent.
Well this is all great except that it's entirely possible that the descent to 2000' is happening a good 10-15 miles from the runway, and the base of the Bravo outside of 10 miles is 3000'.
Ooooops. And as the good
@Capt. Geoffrey Thorpe said, they're now on their own to avoid running down some doof flying VFR. Fortunately Florida doesn't tend to have a lot of VFR traffic.
It seems to be hit or miss whether ATC even bothers to care. Every so often a controller will clear us for the visual with a restraint to be at or above 3000' until 10 DME, or sometimes I'll hear a comment about leaving the Bravo to another airplane. But I bet lots of planes are coming out the bottom and nobody says a word about it. Like I said earlier, until the last couple of years (at least at my company), nobody seemed to be aware of the rule, or didn't much care. But someone in Dallas finally got a bug up their ass about it, a weenie in a cubicle was told to do a study on the visuals into MIA, and they found that a large percentage of airplanes (not just ours) shooting visuals to 12 would pop out the bottom of the Bravo. So next thing you know there are posters in our crew rooms, additional slides in iPad distance learning modules, briefings in recurrent - everything they could do to get us to get our heads out of our asses and maybe take some time to follow the glideslope or (even better) a VNAV path from further out. Not just at MIA of course, but as good practice everywhere*. As you mentioned, since we're always IFR, flight crews aren't typically primed to think about airspace boundaries.
*Pilots blindly bombing down to the FAF altitude when cleared for a visual can be a much bigger problem than simply airspace considerations, but that's a discussion for another thread.
