Is it BS? Yes. Is it necessary? Yes - but not to you.
Big companies are run with other people's money. These people don't trust you and/or your boss(es) any further than they can throw you. I don't blame them frankly. There have been far too many examples of why they are correct not to.
So these other people figure that the best way to safeguard their money is to make sure that you and your co-workers are legit. The only way they can do that though is by hiring yet more people to ensure that you actually tell them the truth about what is happening to their money. It's these third parties, the "auditors", that run most large companies.
Auditors have found that there is a certain set way of running companies that tends to result in the least amount of risk to the money that funds the operation. The money that belongs to someone else. Auditors ensure that the company is run according to these principles.
Ergo: the fact that some rimjob 3 states over once used iTunes to and IM to run a kiddie porn distribution ring or whatever and caused heartache for the money suppliers of that company means that the Auditors concluded that IM and itunes pose a risk to the other people that supply the money for your company: hence, you aren't allowed to use itunes as a matter of policy.
It gets even better when the government gets their hands sticky as well. Because then you get crap like Sarbanes/Oxley that basically makes being a criminal more difficult by making everything more difficult.
Public companies are not about the product/customer relationship. They are about the investment/investor relationship. You are the investment. Your job is to provide a moderate to excellent growth rate for as little risk as possible.
This is why public/large companies have little incentive to innovate in the same way start ups can, as an aside.