I wonder if internally, Google has recognized a business value-prop for fighting spam:

One might argue that by combating spam and noisy advertising, Google makes its own advertising less likely to get ignored (lumped in with the spam), and thus higher value.

Obviously this is a simplistic perspective, but perhaps there's some version of it that makes Google more incentivized to fight spam than Apple might be. Apple is incentivized by a "what makes for the best user experience" which has a more nebulous set of criteria.