Older receptacles and even modern receptacles and cords do still make use of their holes.
It’s why if the holes are included there is specs they must follow.
This plug makes use of the holes for a solid mechanical connection that will only be removed when you pull on the collar to remove the pin that goes through the holes.
If it’s for manufacturing why are some made without them?
Theres patents out there, I don’t know why technology connection did his own experiments on modern plugs instead of a modicum of research about receptacles.
Not exactly sure, I think it's just one of those things were we "people" have gotten so used to the design and how it's supposed to look, that even if it's not needed we keep doing it.
Since multiple companies manufacturer plugs and connections, some manufacturers may not need the holes as a part of the assembly process. Other may opt not to add them as they do not have a purpose (other then how we perceive a north america plug is supposed to look like).
Funny story, almost all standard north america three prong plug are installed upside down. The third "center prong" or "ground" is actually on the top per the original design.
Most new builds and electricians are opting to install this way now. The orientation has no impact on performance.
the ground should absolutely be on the bottom because gravity.
Not necessarily. You typically want the ground longer so it's the first in and last out. Type G has the ground on top. I vaguely remember hearing that's because if it comes slightly out and something sharp or metal falls on the plug, you want it to hit the ground and not the live part...but I don't know how reliable that story is.
Some electricians started doing it since it became a viral Internet trend to intentionally drop quarters onto the prongs of a slightly pulled out plug.
In history there’s only been a few cases of a fires being started because of an accidental thing falling on the plugs. The breaker trips before a fire would start in almost all cases. Provided the breaker isn’t faulty or something. Which you should be testing regularly as a home owner.
This is the reason, yeah, at least according to what I’d read on Wikipedia (I’d just learned this “funny story” myself a few minutes before reading the comment above). I wanted to see if there was anything that could confirm it, but I’m not paying $70 to purchase the standard (NECA 130-2010) where it may be written.