I've worked on the autocomplete team. It was always primarily a way to shave off some measurable time for users, making searches easier and faster — obviously

I've worked on the autocomplete team. It was always primarily a way to shave off some measurable time for users, making searches easier and faster — obviously a direct interest of Google. (There is also a serendipity aspiration — occasionally helping users formulate better searches — but we never knew how to define or measure success in this.) It did change search statistics but not in way anybody welcomed: all statistical analyses (including the building of the completion corpus itself) became more complicated as you now want to separate the signal of "how many people wanted to search this" from the semi-noise of "how many people chose this from the 5 suggestions at the moment they glanced at the screen". Google "Instant" triggering automatic searches for some completions muddled stuff even more... Nobody would go through that just "to hide" something.