I could be wrong but I suspect that they're spending more to market "Casual" games than they typically spend marketing a "Core" games; what I do think is happening is they're spending far more marketing "Casual" games than they would typically spend marketing games with similar development budgets.
For decades publishers have released (what they saw as) low budget niche titles with little or no marketing and were shocked so see that these games didn't tend to sell well; on occasion, due to a large designer being involved with these games a game would become successful and then the publisher would throw money behind it.
What Nintendo has demonstrated with the Wii and DS is there is an actual market for these "Niche" games but the gamers who are most interested in these games are the least likely to go searching for information about them.
