Questions Regarding the Monsters

I’m interested in everyone’s opinions on this.

So if the monsters are the parents of sacrificed children, then why do some of the monsters look like teenagers? I understand that there are teen parents, but some of them look young enough to likely not have had kids. Like that one who tricked the guy into letting her in through the bathroom window, or the guy who spoke to Julie on the porch of the big house. Along that same line, some of the monsters look too old to have had children to sacrifice, unless they murdered adult children (which doesn’t seem like those kills would qualify).

Any thoughts on this?

Also, am I wrong in thinking that many of the monsters are dressed like they walked out of the 50s and/or 60s? Is there significance to their clothing? My initial thought was that they just wore whatever clothing was available, but they all pretty much look dated. Like one guy is even dressed like a vintage milkman.

TY