Oftentimes (sorry, I did type that with my pinkie in the air…) you don’t have access to the floor beneath your shower in order to install your drain. Not usually a problem unless your drain pipe beneath the floor is hanging in the wind! Okay, not hanging in the wind, but not absolutely sturdy either.
It’s difficult to get a good seal when installing your drain if your drain pipe isn’t solid. It pushes down as you try to push the drain onto it. That doesn’t work. So get yourself some string. Or wire. Or anything else you can wrap around your drain pipe beneath the floor and up through the hole for the drain.
DO NOT use one of your wife’s scarves! Not that I’ve, umm, done that…