It may be the previous mindset that open source was only for use with small scale implementation but with many big industries eying the potential in terms of savings of open source development it has entered the mainstream of the computing industry. Many industries such as one airline owned by a rogue British businessman has expressed great interest in applications developed on open source platforms.
Savings that amount to a fraction of what a software system used to cost can be substantial, with no need for extensive and expensive licenses. Support becomes an issue though for should the problem be with the platform, which is not owned by one company but rather a community of individuals and companies it becomes quite vague in the long run in that area.