They also made Audrey Mr. Mushnik's daughter, and made Seymour not an orphan. Plus, they made a cartoon based on kid versions of characters from an 1980s musical based on a 1960s Roger Corman horror movie, and made the plant eat things that weren't human blood. I don't think they cared all that much about staying true to the source material.
Oh, I guess Seymour wasn't an orphan in the original movie - he lived with his hypochondriac mother. That and a few other things remind me that this was based more on the Corman film than the musical version.
Which makes a lot of their choices even more baffling, frankly.