A very simple reason...
Satellites are required at Geostationary Orbits.
What is a Geostationary Orbit?
A geosynchronous orbit is a high Earth orbit that allows satellites to match Earth's rotation. Located at 22,236 miles (35,786 kilometers) above Earth's equator, this position is a valuable spot for monitoring weather, communications and surveillance.
At geosynchronous orbit, however, the orbital period of the satellite matches the orbit of the Earth (roughly 24 hours), and the satellite appears virtually still over one spot; it stays at the same longitude, but its orbit may be tilted, or inclined, a few degrees north or south.
What are the benefits of Geostationary Orbits?
A satellite in geosynchronous orbit can see one spot of the planet almost all of the time. For Earth observation, this allows the satellite to look at how much a region changes over months or years. The drawback is the satellite is limited to a small parcel of ground; if a natural disaster happens elsewhere, for example, the satellite won't be able to move there due to fuel requirements.
This is a large benefit for the military. If, for example, the United States is concerned about activities in a certain region of the world — or it wants to see how its troops are doing — a geosynchronous orbit allows constant pictures and other surveillance of one particular region. An example of this is the United States' SATCOM 5, which launched in 2013. Joining a "constellation" of four other WGS satellites, it extends the military's communications system to provide blanket coverage over virtually the entire planet. The network serves troops, ships, drones and civilian leaders and is supposed to provide communications for ground personnel.
is There a limit on how many satellites can be in a Geostationary Orbit?
YES
At geosynchronous orbit, the “ring” around Earth can accommodate a number of satellites — 1,800 altogether . So far 400 Satellite slots are occupied. These slots are available to all the countries of the world. Pakistan was allowed 4 slots however Pakistan was striped of 2 slots as she could not occupy them. The PAKSAT & PAKSAT-1, are pakistan weather and communication satellites.