The problem for me has to do with the nomenclature. The term "casual" has evolved to mean distilled and/or dumbed-down, when traditionally the term was used to define games that do not require marathon sittings to play. I'm not up on my gaming history, but I believe the distinction between hardcoe and casual games evolved out of MMOs and some FPSs as a way to distinguish them as more time-consuming than average single-player games. In time, however, "casual" has gained a negative connotation which
does imply a simpler game that caters to the largest audience possible--casual gamers. As the gaming industry grows and as businesses realize how much money is at stake, the trend is to make games that appeal to wider audiences than they have in the past, thereby necessitating games that are user-friendly and easier to jump into (and out of). This has, I think, both good and bad implications for gaming. On one hand, more players equates to more money in developers' pockets that they can then spend on more games. On the other, appealing to everyone necessarily means it isn't perfect for anyone.
Casual games
have had an impact--both negative and positive--with the trend toward negative.