Probably some of them do, but we don't see it - we rarely do.
But this guy has shat himself right through his undies and trousers and down his thighs, and this guy has squirted his last shit into his excellent orange undies as he was dying - probably both also squirted their cuum into their underpants as their final act whether or not they were fully erect. As no doubt did many of the others though we don't see it. As why not - yiu onmly hang yourself once, so best to do a good job of it with all the trimmings