Say I use a DDoS prevention service (like cloudflare). They get my user data, and also have to be under scope of GDPR as well. And since IP isn't indicative of EU citizenship status, a company had better apply GDPR to everything rather than just a subset.
In the end, this law makes a "We respect the privacy of your data" subset of providers, and provides a great way for us users to identify bad actors (Google, FB, Amazon, etc).