How well did you really think this out? It only took me a couple seconds to figure out a reason why this feature would be beneficial: it could be more accurate in many circumstances.

And it could be less accurate in many other circumstances. That's why you provide the original data and maybe also the snapped data, and don't just make the original inaccessible. (And worse, tell no one you're screwing with the data you're giving them.)

It could save on battery power: If the user has been on the road, we can ping the GPS less often on the assumption they'll be mostly moving along one of a set of known paths.

It could compensate for poor GPS availability, by allowing the track generator to make more informed guesses about where the user has been, if a GPS ping happens to get dropped.