Legal reasons, probably not-- reasons of aesthetics, yes. Today, the general public pretty much prefers tall and slim speaker designs (see Wife Acceptance Factor). Horns can take up a lot of floorspace- which might limit their appeal these days. The lower the frequency range they reproduce, the bigger they get.

Yes there are- but I'd have to defer to the horn experts out there to tell you why.
There are many speaker manufacturers out there that utilize horns in their designs. Even Altec Lansing (See soundhound's photo) is making the Altec 7 Voice Of The Theatre once again ($4000 each!). You can get horns from JBL- in their Pro Audio series, I believe. Do a search for horn speakers- you'll find lots of 'em out there!
Personally, I like the sound of horns. Our first "serious" speaks were Klipsch Heresy's- the only Klipsch Horns we could afford when we bought them in the late 70's. I just don't see Outlaw hooking their horses up to the old Horn Wagon, but who knows...