I like to think of open source as solving a real problem for people and saving them a lot of time for free, otherwise they wouldn't use it. This often does have the effect of creating demand for complementary services that solve even more problems and save even more time, or even opening up whole new markets like Docker did with LXC.

Anyone considering the addition of open source to their stack should also consider the downsides such as cost of fork and technological lock-in in addition to the benefits, and based on the rapid adoption of open source over the past decade I'd say it's a pretty good trade-off in a lot of cases.