There's still quite a bit of work going on in various directions; "simple theory on big data" is just one of many research agendas in statistics/ML, and it's not really the majority one (though it gets quite a bit of press). It's what Google pushes in part because it's their competitive advantage: they have more data, and the ability to access/manipulate it in reasonable time, than many other places do, so it makes sense for them to see what they can get out of it.
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There's still quite a bit of work going on in various directions; "simple theory on big data" is just one of many research agendas in statistics/ML, and it's not really the majority one (though it gets quite a bit of press). It's what Google pushes in part because it's their competitive advantage: they have more data, and the ability to access/manipulate it in reasonable time, than many other places do, so it makes sense for them to see what they can get out of it.