Fining them after several years of the bad behavior doesn't un-share the data, which means even the "first time warning" should be painful enough so that they don't chance it next time.

If the fines are cheap, companies have every motivation to try and see if they get away with shady or even knowingly illegal behavior - if not, the fine won't hurt too much and if yes, free profit.

If the fines hurt even the first time, there's a much bigger motivation to actually comply with the law from the start.