- Fostering start-ups that may just have that next big hit
- Engendering good will in the indie community
- Exposing end users to a wider range of content
Developers take notice of this sort of move, and they're more likely to be attracted to a platform that makes even marginal effort to help them succeed. Google seemed to understand this in their core business practices early on, and certainly with their posture toward Android developers in the early days of the platform.
Now, though, there is no longer a "Just In" category in Google Play and there never was a dedicated indie channel, so since indie's can't afford massive marketing budgets exposure is virtually zero for a new title. This has caused the Android segment of Google Play to devolve into preferential attachment, or a "rich-get-richer" dynamic. If someone from Google has data to the contrary, I'd like to see it, but I think it's highly likely that the average download rate for new apps (excluding those that are from major publishers or are ports of popular apps) have declined steadily over the past two years.
Google should learn a thing or two about fostering a healthy developer ecosystem from Amazon.