Why are triple threats No DQ?

In a singles match, if wrestler A gets disqualified, then wrestler B has no one to wrestle, so the match is over and they win.

But with 3 (or more) wrestlers, wrestler B would still have wrestler C, etc, so the match could continue without wrestler A.

So why doesn't it?

I've never understood this, and would appreciate people's thoughts.

(Pic barely related)