And before that the decision to make it was based on the desire to tell a story that involves characters. Reductive reasoning aside is there any other reason why you think mechanics should be the focus of a role playing video game based on a franchise infamous for being about the story and characters first and foremost? I can quote the PHB for you if you would like.
It's a fair point. Whatever the original intentions of Gygax and company, though, there is a divide, as Kanisatha has said. Some see it as RPg, others as rpG. Perhaps some miscommunication is arising from the lack of a distinction between 'story' and 'role playing.' I love a good story, but I really don't care much for role playing (which isn't to say I don't like having some direction over the story in a game).