It doesn't improve a pedestrians welfare, instead it removes responsibility and legal liability from the driver.

Apparently it isn't. We have to build barriers to prevent people from running into traffic because not even the law is enough to discourage it.

I believe the argument is that it may create danger for other people as well. For example, an oncoming car may swerve to avoid striking the pedestrian and hit something else. I'm not sure that's a very likely scenario, however.