Okay, I don't know all the detail, but here is my cut:

For example, Opera is free on desktop, but not on small devices. Companies use those popular platforms to attract users, establish their products and then sell their products somewhere else or complementary products on the same platforms.

For Adobe it's worth spending their money on Flash player for Windows, but on a platform like Maemo, the platform owner (e.g. Nokia) should cover the costs of porting, tuning and testing.