Why do we need make dependencies?

Question

GNU Make

hello: main.c hello.c
        gcc -o hello main.c hello.c

Why does "hello:" need "main.c" and "hello.c" ?
they are on the team.
It turns out that the duplication of information

Answer 1

So that in the event that main.c OR hello.c has changed by the time make is executed, each of them would be recompiled. If this is not done, there is a risk that the source is newer, and the older object module will be included in the binary.

Answer 2

Because in the general case, the command and dependencies are not related in any way.
Specifically, here you can avoid duplication using automatic variables
gcc -o [email protected] $^