From Vostok 1 to date, atmospheric reentry has been essentially passive. Passive here means that retrorockets are used to de-orbit, and then aerobraking is provided by the atmosphere. In contrast, active reentry would mean reentry under engine power (which may lie somewhere in the future perhaps).
As I understand it, this reduces the amount of fuel required to be carried for consumption only on the return journey. Indirectly, it allows more payload to be carried on the journey up — thus good math.
Are there any other advantages to a passive atmospheric reentry / aerobraking?