I thought it might be because they originally parachuted out of the capsule instead of landing in it.
The story I've heard was that this was precipitated by an incident involving Alexey Leonov and Pavel Belyaev, whose landing capsule went off course and landed in some really out of the way place in the northern Ural, making extraction a problem. It took a while to find them, and they had to ski out of the place, since it was impossible to land anything there. They actually had some bears come around, and the Makarov pistol they had didn't particularly fill them with confidence.
Inclusion of smoothbore barrels was intended to make not just a small game hunting gun, but a more effective signalling device.