Castlevania: Belmont's Curse producer Tsutomu Taniguchi explains that he proposed the development of a new game in the series after reading comments from Metroidvania fans who'd never played a Castlevania game.
Castlevania may be the one half of the genre name, but according to Taniguchi, many self-professed Metroidvania fans admit they've never played any games from the franchise. In an interview with Famitsu, he spoke about how development of Castlevania:Belmont's Curse began from this revelation.