I think that there was a pedestrian walkway on the suspension bridge that was not part of Telford's original bridge and it was causing problems with the bridge.
This I think was removed when the bridge was taken over by Cadw.
I agree with Yorkie that it seems ridiculous that this important piece of history could even be considered to be removed. I bet they didn't let the townsfolk of Conwy have a vote when they decided to put that carbuncle on the top of the Town Hall,