Slight departure from formulaic dungeons
In an interview with French publication Lemonde, Eiji Aonuma talked at length about Legend of Zelda: Breath of the Wild and certain things that you can expect from the game. Among those things, Aonuma talked about a departure from previous Zelda games by making this one open world.
Aonuma also talked about dungeons, and how most of them will instead be shrines.
Mind you that this is from a French outlet and translation is mainly done via Google Translate, but it implies that we should not expect the same formula that Zelda has had in most of their past entries about how they associate weapons with a specific dungeon and with a specific theme. It is a possibility that dungeons are still a big part of the game, but that there are a lot less of them when compared to the shrines, which Aonuma stated we should expect more than 100 of them.
Another reason could be that, because the world is so big, you can see specific areas like forests, deserts, oceans, etc., which could in turn inhabit those specific dungeons. As far as the shrines, we can expect them to vary greatly in size.
The full interview can be read here (in French).