There are a number of factors of what have caused this but I don't have the time to write an essay on each one so some bullet points:
- Japanese are tech illiterate, most people don't regularly use PCs and are not familiar with things like SNS sites, IM clients, RSS feeds, modern day forums, PC gaming, etc, rather they use their proprietary mobile phones for a gimped internet experience from 10 years ago
- Consoles have moved from proprietary Japanese architecture/documentation (DC, PS2) to PC dev friendly, more off the shelf parts means that Western and developing country PC devs who have been creating PC titles can easily move their skillsets over
- Global economy downturn trend = less money to invest and less income coming in for the big players (ie look at the dollar yen rate)
- Japanese cultural trends of pussy men (herbivores) dominance have negatively affected the design of pop culture and have created a gap between what Japan and the West find appealing (eg main characters of Gears of War vs cast of FF13)
In summary, Japanese have been behind in tech for years, especially in the PC dev and networking space. This has finally caught up to them as console development has become more PC like and not Japanese proprietary as it has been in past generations. Most developers do not have advanced experience with the graphic tools Western devs and even students use and few companies have money to invest in training their people so the Japanese devs are very much stuck in stagnant PS2/Wii dev processes.