So why don't they do better?
Because no one is forcing them to. If it was in their financial interest to do better, they would. Unfortunately, the federal government has shown zero interest in protecting the Great Lakes. Obama would rather pander to business interests than protect the greatest fresh water supply in the world.
I think it goes much deeper than Obama. The more and more one looks into it, it seems that every single form of government is tainted with corporate interests. From agriculture to the protection of the Great Lakes. It seems like a complete revival of the government is the only option for change.
It certainly goes much deeper than Obama. No doubt. I happen to have a particular distaste for his Great Lakes policy with regard to the Asian carp problem. He could close the Chicago River canal into Lake Michigan by executive order this instant, but he has refused due to his cronies griping about shipping costs. The shipping costs will look like chump change when the entire Great Lakes ecosystem is ruined.
As a publicly-traded for-profit entity, their number one goal is to make money. Safety precautions are costly, and their motivation will largely stop after meeting regulations (to the effect that they are enforced). It looks like the divers found some violations, and hopefully Enbridge will fix that. Regulations are costly for business, but a lack of enforceable regulations can be very costly for the public. Of course, there should be a balance. Here it looks like the public is shouldering a lot of risk on Enbridge's behalf. Sometimes management can do right by the public, making sure that even unenforced regulations are met. Enbridge's history suggests that they don't have that kind of management.
I would hazard a guess that attempts to put those regulations in place would be thwarted by politicians who accept lobbyist money. For a while now, I've felt compelled to work for the EPA. But when I continuously hear how they aren't allowed regulate one thing after another due to outrageous laws, it makes me think that a more radical group like Earth First! might be a more fruitful option.