Earlier quoted context omitted.
One thing I've heard is that this would help them in terms of taxes, allowing them to write off projects that don't make money, although I'm not entirely clear on how Alphabet would accomplish this. That would be no joke if that was a reason to do it.
The first thing I thought of involved the regulations and other troubles that Google was facing in the EU. Those troubles seemed to summarize as "Google is too big and is taking advantage of its large market share". Alphabet looks like it'll fracture the google businesses more, which might help reduce the issues they're facing in the EU. But that's just my best guess
That is also a common (mandatory?) setup, for multinational companies to have a local subsidiary in every country where they operate. I guess institutions like the EU must be handle that and focus on the activity independently of the fine details of the company structure, so that the restructuring would not really help or hinder.
[0] http://www.sec.gov/Archives/edgar/data/1288776/0001193125070...