In short, clustering in the world of visual arts has both an economic and artistic imperative. At first glance, it's hard to see the similarities with game development, especially given the global nature of game consumption. But if we cut the end-user out of the equation and focus on the internal industry side of things, we begin to gain insight into why clusters evolve.
For starters, there are real, hard transaction costs for developers and publishers to do business. If a developer can fly to Los Angeles and see a dozen publishers in one week, their deal prospecting costs are dramatically reduced. Even more so if the studio is based in L.A. and it's a taxi ride instead of a flight. The same is true for publishers working with the holders of licensed intellectual property (movies, books, comics, etc) - it's much easier to do your one-stop IP shopping in Hollywood.
Similar transaction costs come into play for talent, both from the employer and worker perspectives. As noted above, access to talent is a key factor for the establishment and growth of studios - no talent, no games. It is critical for studios to have easy access to a pool of talent - both internally (e.g., poached from other nearby studios) and externally (students or veterans from related sectors). Interviewing and importing talent from abroad is an extremely costly proposition.
Costs to the worker are critical as well. If a programmer can live in a city rich in development studios, he or she can move from job to job with relative ease should the need arise. The personal risks are far greater if he or she needs to move cross-country to a city where there is only one viable employer. Even labor laws come into play: Employment in a region such as California, known to have very worker-friendly labor laws, is preferable to a region famous for the brutality of its non-compete clauses. Just looking at recent layoffs, the ability of a region to re-absorb talent is critical - especially from the workers' perspective.
Finally, a community of local professionals is important for its own sake, with major clusters often supporting vibrant informal networks for peers to exchange ideas - and gossip. Such communities provide an important aspect of personal and professional development. A city devoid of such opportunities becomes more risky and less appealing to workers.
These are just a few ingredients, and we've only begun to explore the complex interactions that create an ecosystem, or cluster, of this kind. It requires a nuanced and holistic approach to understanding the dynamics of such communities. It's not as simple as getting government hand-outs.
Ultimately, success can come from anywhere, even Costa Rica. But you can be sure, there's a higher probability of success in a cluster region. The good news is that if you don't have one, you just might be able to grow your own!
Jason Della Rocca is the soon-to-be ex-Executive Director of the International Game Developers Association (opinions expressed do not necessarily represent the IGDA). Jason blogs from clusters around the world via RealityPanic.com.