Sometimes the projects and developers can rotate like they do in Hollywood, but even so, there's no Ari Gold, because the companies stay the same.
In London's finance industry, there are actually many contractors often working on temporary projects of a similar lifespan to a hollywood movie. The difference is the relationship with the third-party recruiters. The companies and their HR departments will still be around afterwards, similar to the point you're making here, so they establish long-term relationships with the agencies/recruiters. Thus, the agency is biased towards serving the needs of the company. It sees the company as its client, not the contractor. A lot of the time they can get exclusive assignments this way, and with many exclusive assignments around, it's not in the interest of a developer to be tied exclusively to any one agency.
In London's finance industry, there are actually many contractors often working on temporary projects of a similar lifespan to a hollywood movie. The difference is the relationship with the third-party recruiters. The companies and their HR departments will still be around afterwards, similar to the point you're making here, so they establish long-term relationships with the agencies/recruiters. Thus, the agency is biased towards serving the needs of the company. It sees the company as its client, not the contractor. A lot of the time they can get exclusive assignments this way, and with many exclusive assignments around, it's not in the interest of a developer to be tied exclusively to any one agency.