The theory is that BP cut technical and engineering corners for the sake of saving time, aka profit.
All of these companies could do the same, to great potential public harm.
Say Windows ships with a flaw that causes all machines to shut down at noon on a certain day. Or Apple ships an entire generation of phone that puts out a high level of radiation in certain circumstances. And so on. Amazon sells computing instances. Google has fingers in nearly every pie out there.
These companies can cause significant worldwide harm, financial and in some cases physical.
What if they cut corners to meet goals and endanger people as a result. Do you really believe this will never happen?
My problem with the BP situation is that the risks were fairly well understand as oil is a mature industry. I expect BP to be fully liable for their negligence just as I would expect Apple to be fully liable if they released a radioactive phone. Do you think BP is being held fully liable?