There's a good reason for that: by rights an exe file doesn't contain enough information to convert to a C file. Obviously, for instance, no necessity of containing variable names, data structures etc. In fact the C syntax definition doesn't limit how a compiler goes about making it work. It can't, because otherwise C would become platform specific... There's no hard and fast rule that says a computer must have its memory arranged in a certain way, or a byte-size of 8 bits, or whatever, yet any machine should be able to run a C compiler if someone cares to write one.
Therefore it would be very hard to write a C decompiler, because the piece of code resulting from a C statement might not be the same from all compilers. In fact a C compiler could happily make a runnable exe file that could equally well have been generated by a fortran compiler.
And the original author might have used any number of commercially available libraries etc.
Any good author will have laid out their program according to some sort of good practice, but this reflects only in the readability (and bug content!) of the program, not in the final compiled code. Therefore a decompiler would need to play at psychology to guess how the original might have been written.
I suppose you could, in theory, write some sort of C decompiler, but it would probably produce really nasty code that's hard to read. Frankly, I think most people use disassemblers not to produce compilable assembly code, but to see what their compiler is making of code they already wrote, or suchlike poking around.
Wouldn't it be nice to be able to decompile, though!
Sorry to have such a lengthy rant, but this question has come up a few times before, so I thought it deserved more typing than normal.
