Flat fines often don't work well in accomplishing their sole purpose, deterrence.

If high enough to deter the better off, they will unjustly burden the lesser off. If minimal enough to be affordable to all, they don't sting enough for the wealthy.

Unlike taxes, which are a fee for services rendered and thus should be flat across all who use those services, monetary penalties should be proportional to income to ensure they can deter in a just way. Many Nordic states use this system for traffic fines and it seems to work well.

The question of automated systems being used in law enforcement, which put the burden of proving innocence on the accused (particularly when the "witness" against them is a machine) is a different issue.