My guess is there was a cost-benefit analysis done that says, yes, hundreds of thousands of tug boat runs are cheaper than a bridge collapse. But for a bridge collapse you would need an absolutely massive vessel to hit a support beam, and that ship would have to have a catastrophic failure of infinitesimal chance to occur. Therefore, no tug boat runs under the bridge.
Unfortunately, the roll of the dice came up bad.
I don't think a bridge can be built to take a hit like this. I think the review of this incident will point at further redundancies needed on the vessel itself.
Catastrophic failures will always happen. Just have to do everything we can to prevent them.
