The distinction between casual and hardcore games was probably first developed by nerds who thought that their "leet skillz" at gaming were being infringed by grandmas and parents who found that they could do pretty damn well at zynga games. Their supremacy over games threatened, the nerdiest parts of gamer sub-culture created the distinction so they could salvage their egos.
Honestly, there is no reason to place any distinction between games that are named casual or hardcore. Yes, they are not the same from title to title but no game is really identical to another unless made as a direct sequel or HD remake.
Games are games. Some are complex and some are simplistic in their design but, so long as they are enjoyable, they are just games.
Also, if you see advertising for a game that relies on catchphrases like "The newest and best game for the HARDCORE gamer" then you will have just noticed that the advertising departments are using customer and party loyalty in order to get you to buy, buy, buy.