Rodney Greenblat wanted the show to be aimed at Teens, but because Sony wanted to sell toys, they made it for kids.
Originally, various characters from the games such as Lammy, Ma-San, Joe Chin, and others were going to appear in the series, but because the show was aimed at kids, and wanted to sell various merchandise, they were cut from the show. This is also the reason why PaRappa doesn't rap in the show.