Why SIGSTKSZ is often mutiplied by 4?

I've noticed that a lot of repositories do not use just SIGSTKSZ as alternative signal stack size but multiply it by 4. Examples:

Code from here:

#define STACK_SIZE 4*SIGSTKSZ
char wad_sig_stack[STACK_SIZE];

And from here:

size_t FatalConditionHandler::altStackSize = 4 * SIGSTKSZ;

But man tells: The value SIGSTKSZ is defined to be the number of bytes/chars that would be used to cover the usual case when allocating an alternate stack area.

So why the most common alternative signal stack size is 4 * SIGSTKSZ?