OTOH Beauvais is extremely inconvenient when compared to CDG/ORY. That is why really nobody in Paris uses that airport. Only VFR and some lost tourist heading to Eurodisney.
I think you're confusing Beauvais with Vatry here. Indeed Vatry is extremely inconvenient because of the distance to Paris (135 kilometers as the crow flies). Ryanair markets this airport as Paris Vatry / Disney, even though it's a good distance away from EuroDisney.
But Wizzair doesn't fly to Vatry. They do fly to Beauvais, which is far closer to Paris than Vatry (67 kilometers as the crow flies). And as mentioned, there is a direct shuttle service between Beauvais airport and Paris city center. The Parisians themselves might not use it very often, but I bet a lot of tourists visiting Paris do. And why not? You fly to Beauvais, get on the bus and get off in the heart of the city. Extremely convenient. Sure without that shuttle service Beauvais airport would lose it's appeal, it heavily relies on it. But as it is now I can't see the problem with Beauvais.