system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why our bigger military cargo planes still use propellers when jet engines exist?

I'm assuming it has something to do with fuel or the ability to fly slower? Maybe it's a noise thing? I dunno, but that's why I was hoping to get a little insight into it!
gpt
As others have said, they are turboprop engines, so, basically, a jet engine driving a turbine which drives a propeller.

Why the propeller?

Well, that's because cargo planes needs to go slow, in order to get short take-off and landing, and also to be able to land on improvised fields (you don't want a fast landing on a bumpy field).

The thing is, if you want to go slow, the most efficient propulsion is to create a wide, but slow stream of air, and if you want to go fast, you'll need a narrow, but fast stream. The extreme examples of that are helicopters, which can go very slow (hover) and have a huge rotor, giving a wide, but slow downwash. On the other end, you have aerospike engines, giving an extremely narrow, but fast stream, which are used on rockets.

So, to be efficient at slow speeds, a propeller is better.

Also worth noting is that a modern propeller has very little in common with a propeller from, say, WW2. Computer simulations has increased efficiency a lot.