I don't think privacy has anything to do with it. Google Maps doesn't need to capture any user data to implement OP's suggestion. Google Calendar just needs to render a map with a set of locations marked on it using Google Maps. It doesn't need to tell Google Maps what or who the locations are for. This is something Google Calendar should already be able to accomplish using a public API. All other aspects of the feature could be implemented as part of the Google Calendar service without any further integration with Google Maps.
Further, I don't think users are generally against services using the information - which the user has presumably already provided intentionally - to better serve them. The problem is when that information is shared with third parties or used for purposes which are not obviously in the users' best interests. IMO, any user data stored externally should be subject to an opt-in permissions system which strictly defines how the data can be used. That doesn't stop companies like Google from being able to offer me useful services that I might actually be interested in. The notion that privacy discourages innovation is just silly.
Further, I don't think users are generally against services using the information - which the user has presumably already provided intentionally - to better serve them. The problem is when that information is shared with third parties or used for purposes which are not obviously in the users' best interests. IMO, any user data stored externally should be subject to an opt-in permissions system which strictly defines how the data can be used. That doesn't stop companies like Google from being able to offer me useful services that I might actually be interested in. The notion that privacy discourages innovation is just silly.