Yes - the social construct is that we are partnered - and that if we are forever non-partnered, something is wrong. As you note, we are animals - social animals, too. And so, the expectation is that we should be partnered and also in groups - and if we're not, well, that's "not normal." Using these signals (husband, bf, gf, wife, etc.) - these tell other humans that we are not so terrible we should be avoided - it's like an entry ticket.