Because women are needy. I have seen women stay in horrible relationships, never one did they say I am leaving this asshole.
There is no way I would stay in a bad relationship, but I don't have self esteem problems either
Because men no longer know how to truly be men.. lol. Seriously though, most men no longer know how to take responsibility for their actions, or stay true to their commitments.. so they walk away. There are women who do this as well.. but not nearly as much as the men do it.