There are, in fact, many reptilian groups, offshoots and splinters scattered throughout this part of the galaxy. The term "Dracs" is usually refers to the main body originating at and around the Alpha-Draconis star system, and their organized activities.
They are meat eaters and find humans "tasty." They also find cats, dogs and cows to be very tasty. Their fondness for earth-based proteins is certainly part of the reason for their pursuit of Earth right now.
They also traffic in various rare metals and even some of the manufactured goods humans are capable of making at this time, some of which do have value in certain markets, particularly among the Syndicates and black market zones.
There is a minor political group among the Dracs who contend that the Earth is actually theirs, anyway, because their biologic ancestors originated on Earth itself, though something over 70 million years ago, prior to the last major impact event.
MIBs: this is a view spoken of only by a minority group of the Dracs. Though not denied by any, most seem to hold it as irrelevant. MIB archivists are unable to verify this claim, in any case. Nor does it seem likely that any species on the Earth during that time would have been capable of space fight, thus preserving themselves in spite of the impact event that devastated the planet for millennia afterwards.