The damage is done before you can run a correction. It can affect not only the buying and selling of stock, but also whether a company can borrow on the credit markets. A simple, honest mistake on deadline can ripple out to harm a company before the reporter even gets home. It's always important to get it right. But it's even more critical in the financial press than in general, non-business news.
General news tends to be an accretion of information over time.
Take political coverage. You can get it wrong on Tuesday and correct it on Wednesday, and the only impact may be a temporary blip in tracking polls. But every political reporter knows that extra care must be taken in the days just before an election because a last-minute bombshell can affect the final result. Financial reporters need to take the same care every day as political reporters do leading up to Election Day. The risks are the same.