Even a cash-only business with no electronics anywhere would still need nontrivial GDPR compliance efforts because it has employees. Just because you need the data to run your business doesn’t automatically make you exempt without further paperwork. Your lawyers definitely do occasional GDPR compliance work.
https://www.dickinson-wright.com/news-alerts/the-gdpr-covers...
It’s a bit like accounting. You can structure your business operations is ways that make the accounting easier or harder, but unless you shut the business down you will always have done enough somewhere to need to think about (and probably file paperwork for) accounting/GDPR. And much like accounting, I’m not saying the GDPR is bad, but it’s also not a business activity that you can just ignore because you’re not running an adtech data vacuum or whatever.