Russian capsules launch from the Kazack steppe. In the event of a launch abort, like there was in October 2018, you need to have a capsule that can land on land.

American capsules launch from Florida and fly over the ocean. In the event of an abort, they need to be able to land at sea.

They both took their abort modes and just made it the standard way to land after a mission.

I imagine a lot of factors... but yeah that's a big one, no mountains, no buildings, no population centers, you can miss by 100 miles and just add some time to the recovery.

There are so many things that you can land on land that will absolutely ruin your day. A large boulder, a large tree, a cliffside, a building, something flammable, near an angry hungry bear... Astronauts coming back to Earth after spending a significant amount of time in microgravity are also mostly helpless until they adapt to Earth's gravity again. The open sea is seen as safer in the American school of thought.

The capsules can do a water splashdown with parachutes alone.

The capsules that land on land all seem to have some additional system to slow down in addition to the parachute. Boeing Starliner has airbags that deploy around and below the heat shield. Soyuz has a braking rocket system that fires immediately before impact.

So, the issue does come down to the chutes. A chute capable of reducing decent speed to 10m/s is significantly larger than one capable of getting the speed to 60 m/s. Impractically large on a weight constrained thing like a space capsule.

The Soyuz uses a small set of retro rockets to reduce speed in the last few seconds before touch down, and even then it’s like being in a car crash.

On the Vostok capsules the astronauts didn’t even land with the capsules, they just bailed out and parachuted down.

Landing in the ocean is significantly more comfortable and less complicated.