Back then is back then; the world is, as they say, changed.
More gamers, different standards. If you re-released a 2007 masterpiece today with no updates to its graphics it wouldn't do AAA sales. Today's AAA games are more like films, with blockbuster film budgets and timelines.
It's perfectly true that no-one is forcing them to spend such a huge amount of money. But in another sense, economics strongly strongly encourages someone to do that, because doing so is profitable compared to not doing that.