Some conventions are socially made... In C, some uses

#if 0

    these_lines_are();
    not_executed();

#endif

but most of the cases people just use

/* comments

* these_lines_are();

* not_executed();

*

* end comment */

Then, why?

#if 0

#endif

looks clear and it definitely says how a computer skips many lines.

But we just don't use it because it implies low-level knowledge "that every C developers have"