Why does the A380 not have front windows on the top floor?
(flightglobal.com)

You'll need to zoom above 100% to read the legend, but up there it's not empty. There's the crew rest area (5), where the pilots rest for example, and it is easily accessible from the cockpit (see below for how it interacts with the upper deck).

There is also an electronics bay (29), and toilets (12).

Note that the cockpit is not on the main deck, it's between the main and upper decks, the mezzanine if you will.

Design-wise, the forehead is very sloped for aerodynamics, so to offer a forward-facing window view (if the area was empty), there will be an enormous unused legroom (for head clearance). The view also wouldn't allow seeing a big distance ahead and below, so it will be more like a skylight window, especially that airliners typically cruise with the nose pointing above the horizon. And with the area clear of walls and supporting structures, the plane will gain weight to strengthen the shell in that area.

For the secondary question see, 'Has any passenger airliner ever offered forward-facing windows?'


(source)