Sucking up 4% of revenue is catastrophic enough (that is probably double digits of profit). The goal of fines isn't to make be an extinction level event for a company.
Why not, out of curiosity? We don't make this distinction for low-income folks who get parking tickets. If you don't make them truly punitive why comply? It just gets factored into the cost of doing business.
But fines and tickets being pegged to income is a good idea. Fixed amounts for fines are really expensive if you don’t make much money. Similarly, they aren’t much of a deterrent if they are a small amount of your income.