I think the choices people make around this can be put down to child personality (how clingy and/or destructive they are when left alone) and parent personality (more or less bothered by crying and/or potential damage to house/child by being left alone, more or less bothered by toileting alone).
To me toileting alone is not really important (although would not be entirely happy for strangers to see me on the loo). It's not some horrible secret to harbour. We all have bodily functions! DS can come in when I'm in the toilet (he did almost always when younger - he followed me everywhere), but the mostly doesn't now (he's 3.3). I still leave the door ajar. I'm trying to remind DH to leave the door unlocked so that DS can come in with him if he wants, as well, so that he doesn't think that only women go to the loo. Or that men going to the loo is somehow more of a disgusting secret 
DS not potty trained yet, as he's just not interested. I'd actually LIKE for him to come in with me more often so we can chat about pees and poos to try and get him interested in it!
If I was to shower when he's up, he'd want to get in with me, which is fine, as well, but will take longer. So, if I'm not in the mood for a long shower, I will save it for when DS is in bed.
But then again, I'm Northern European. You can put this "being relaxed about body issues"- business all down to that, if you wish to see it as abnormal.. Although I'm half Southern European, as well. So maybe not!