I don't really find that especially surprising but I wouldn't necessarily generalize it beyond Manhattan. Manhattan had an imperfect but certainly widely used taxi system--culture even--before Uber came along. The Uber experience may well be preferable to the taxi experience but the difference is probably not such that a lot of people who were driving private cars to avoid cabs now suddenly stop driving. And a lot of people who live in Manhattan don't even own cars in any case.

I would have expected some impact on traditional black car service but that may be such a small slice of the total that it doesn't show up in the numbers.