The difference is, with a decent voting system, it only takes 51% of the population to decide government policy, but with corporations, even 1% of the population can keep harmful corporations from bankruptcy.

Even ignoring the problem of those 1% potentially being the richest 1%, there is the issue that harmful businesses often have lower costs than ethical businesses, and some consumers are too price-sensitive (or don't have time to become informed about every corporation's business practices) to vote "correctly" with their purchasing power.