Why do different branches of the military use different planes?

I'm a bit of an aviation enthusiast and I've noticed each military branch has its own collection of aircraft. Why do the different military branches need to use different airplanes? Don't they all basically serve the same purpose?

In essence, different branches of the military use different planes because they have unique mission requirements and operational environments. Each branch has its specific duties and roles in the defense framework, necessitating distinctive equipment, resources, and aircraft types.

Take the Air Force, for instance. It's primarily focused on air superiority, long-range bombing, air-to-ground support, and airlift capabilities to transport troops and equipment. To fulfill these diverse roles, they utilize an array of aircraft like F-22 Raptors for air superiority, B-2 bombers for long-range strikes, and C-17 Globemaster IIIs for air transport.On the other hand, the Navy requires planes that can operate from their aircraft carriers. They need jets that are rugged, compact, and equipped for carrier operations. Aircraft such as the F/A-18 Super Hornet are designed to operate both in air-to-air combat and in bombing missions, all from the limited space of an aircraft carrier.

The Army primarily uses fixed-wing aircraft for transport, surveillance, and communication roles. They primarily rely on rotary-wing aircraft, like helicopters, for transportation, medical evacuation, and close air support missions.The Marines need multirole craft capable of supporting amphibious operations and providing air support to ground units, so they utilize planes like the F-35B, which possesses Short Take-Off and Vertical Landing (STOVL) capabilities.

The Coast Guard, though smaller in size, also maintains a fleet of fixed and rotary-wing aircraft. Their planes primarily focus on search and rescue, maritime patrol, and law enforcement. They have specific aircraft like the HC-130J for long-range search and rescue, and MH-60T Jayhawk helicopters for missions closer to shore.

In short, each branch has a different set of responsibilities and operational environments, so they each require different kinds of aircraft to perform their individual missions effectively.