[jack_pp]

Because a model like this can't be as easily obfuscated as image processing. Image processing is a bundle of many moving parts, a lot of functions each with it's own inputs and outputs. A model is a single function which can be easily extracted and reused, in comparison

[Aachen]

Arguably, but that's not the point. Take image (e.g. png) files on a CD-ROM shipped by a game vendor, which can be trivially copied even by my grandma. That doesn't move the game vendor to release them as freely distributable under the Apache license

[jack_pp]

Good point but still, why would Google police this model? If they had a restrictive licence on it do you think it would be worth it for them to enforce it? This way they at least buy some good will and mindshare

[Aachen]

That makes sense to me. Guess one might say the same for game icons and other such files that lay around in disks, but yeah maybe it's as simple as that

[jack_pp]

Not quite the same, understandably Blizzard cares a lot about their IP because otherwise private servers leech their users. Maybe a small game designer cares a lot about the small game they made or whatever since that's all they have. A four trillion market cap company can afford to be "charitable".. where it costs them nothing and might cost them more to enforce their rights.