The Ebon Hawk and the One Hit Wonder aren't the same class of ship.

http://www.starwars.com/databank/starship/ebonhawk/index.html

http://www.eyrie-productions.com/UF/FI/SOS/1HW/

As far as Daggerdisc and the Millenium Falcon, their spaceframe is from a rather ubiquitous line of cargo ships, so you're bound to see quite a lot of them (though Daggerdisc is slightly more unique than most). It'd be like saying, "Gee, there are an awful lot of C-130's flying around." It should be more surprising, in fact, that there aren't more named of the class in UF, but there are so many other starship classes to choose from that that would be boring. :)