Answer 1

because getchar([type]) is not defined in the C standard

Answer 2

Well if you really want it the other way...
#define getchar(c) c=getchar()

But you should probably just use c=getchar() to be honest ^^

Answer 3

Because thats just not how it works, not sure of the parameters, but it returns the next character in the stream. try:

a = getchar();
printf("%c\n", a);

Answer 4

because it's meant for a different use

Answer 5

the person/people who wrote it decided it and we just accept it and use it or write our own if we don't like their's ¯\_(ツ)_/¯

Answer 6

haha