Self-scans reveal that Pegasus, an invasive and powerful spyware that can secretly control phones and track owners, might be more widespread than previously thought. It was discovered on the phones of everyday phone users.
From wikiHow: How to Check Your Smartphone for Pegasus Spyware
It technically uses various zero-day zero-click exploits to get there. Which is why it functions like a service - they need to maintain relevance of those exploits. Imagine, a whole service of clearly illegal activity, which doesn’t get absolutely destroyed simply because it’s useful to spy on dissidents.