Here's why:

* Size: The Pacific Plate is the largest tectonic plate on Earth.

* Location: It's mostly located in the Pacific Ocean basin, where oceanic crust is prevalent.

* Volcanic Activity: The Pacific Ring of Fire, a zone of intense volcanic and seismic activity surrounding the Pacific Plate, is a testament to the ongoing formation of new oceanic crust.

While other plates like the North American Plate and Eurasian Plate also have significant portions of oceanic crust, the sheer size and location of the Pacific Plate give it the highest percentage.