In many cases, it's much easier to prove that a corporation did something illegal than it is to research who exactly in the corporation was responsible (except for the CEO, of course, but to hold the CEO criminally liable for everything a company does would be too open to abuses).

A primary (if often unstated) function of corporations is to diffuse individual responsibility and accountability.

Decisions -- where they are rational -- become a cost/benefit analysis. If you really want to deter the behavior, the costs have to outweigh the benefits. (Perhaps significantly enough to outweigh various arguments about what the true costs and benefits might be.)

And... this still says nothing about the damage that may have been caused to victims, and compensation for same. (For example, take someone's health away in certain fashions, and no amount of money can replace it.)

Serving time for a purely corporate offence is very very rare. Health and safety negligence is most common, but even the horse war scandal in Europe (where unfit horses were sold as beef and then into ready meals) it's unlikely and people there committed fraud as part of course of business

That's a matter of prosecutorial discretion. The point is they can serve jail time. What's the point of changing the law so that they can be fined 100% of revenue. The same discretion will still apply.