Don't know why. All I know is that I've used three low-end forks and with the lockout on, they still could be compressed. I honestly didn't notice that much of a difference either way and would have no idea whether it was on or not, so I just left it off. I notice a difference when it's on with my more expensive fork, but the ProPedal works well enough that whatever, I don't bother, I'm happy with that. Last fork I bought doesn't even have lockout...I just don't care enough about it as a feature.