I would certainly be in favor of that. But from the developers standpoint, I would imagine that those "Casual" gamers don't have the patience that we do to adjust sliders. So they default to them.
NHL 2K5 (or maybe 2K6) had a pretty good idea...how well it was implemented is debatable, but the idea was good. But they had some preset settings for Sim Game, Arcade game and I think there were a few others too. Beyond these presets, sliders were available for further customization.