Class B DEN -- is out in the middle of nowhere, nothing urban anywhere
around, 20 miles from downtown Denver. Almost entirely agriculture in
the 10miles around it, what's better known as "Area of Influence".

As for "special training", I always thought that's what I learned in
my ASEL training.

And as for flying a piper thru downtown NYC, have you bothered to take
a look at the flight paths to JFK from the west? Directly over
the center of Manhattan. In fact, if you examine the flight paths
of most aircraft coming/going to Class B airports (again, DEN is
an exception due to its location) you'll find almost every aircraft
is routed directly over high-density population areas. LAX, from the
west, doesn't have quite as severe a problem (ocean, you know).