User blog comment:Megadracosaurus/Where are the Dragons?/@comment-4211718-20140712185507

Budgetary reasons I think would be the reason, at least for not showing dragons living all over and in and out of Berk....though that's no excuse for not acknowledging their presence in the writing or having the characters talking about them and acknowledging their existence. The general lack of acknowledgement for all of the other dragons except for the five main ones and Thornado has always been what I felt is the weakest aspect of the show and the biggest flaw it has.

Personally, I'd just assume that they're there regardless of what the show says or doesn't show. One thing to keep in mind is that the show wasn't actually written by the writers for the movies and didn't have that much involvement from them to my knowledge. It's entirely possible the people responsible for the show have slightly different views on the dragons when it comes to Berk than the writers for the movies/shorts. I'd just go with what's shown in How To Train Your Dragon, Book of Dragons, Gift of the Night Fury, Legend of the Boneknapper, and How To Train Your Dragon 2 when it comes to all of the dragons and how the people of Berk interact with them.