Here's why:

* Gravity is a function of mass and distance. The more massive an object, the stronger its gravitational pull.

* The universe is incredibly massive. It contains billions of galaxies, each with billions of stars, planets, and other objects.

* Gravity is additive. The gravitational pull of all these objects adds up to create a massive overall gravitational force.

While black holes are incredibly dense and have immense gravity, they are still smaller than the entire universe.

It's important to note: While the universe as a whole has the most gravity, its gravitational force is spread out over vast distances. This makes the overall effect of the universe's gravity less noticeable on a local scale compared to the gravity of individual objects like stars or planets.