It's a (relatively) inexpensive marketing tactic. Some people stick around and become paying customers. This has been a much more effective way at building market share than something like advertising with Google. Even if there is also nefarious intent, which there may be, you have otherwise clearly laid out legitimate reasons for giving away free games.

It's a (relatively) inexpensive marketing tactic. Some people stick around and become paying customers. This has been a much more effective way at building market share than something like advertising with Google.