Is A Rotated Die Error Common?

On further review, it scales out at a whopping 9.8 grams. Ouch.

Ah, well. I guess I will save it, as April 1st is just around the corner!

I guess that. if you look closely at the rim of the two obverse sides, it is fairly obvious.

Why do people waste their time doing something like this?

Yes this does happen frequently but not usually as much as the one you show. True it might be a put together one but if it is, was done for some reason. For example those many 2 headed or 2 tailed coins. Not sure if yours comes apart but if it does it is part of one of the many magicians coins used to do things.
As to rotated reverses, they are really more common that people think. And in some coins really common. Mercury dimes I've found about 255 have rotated reverses to anywhere from slight to excessive ratations. Buffalo nickels too appear to have that problem.
It usually goes unnoticed for one main reason.
Take any coin in your hand and try to turn it over EXACTLY. By that I mean turn it over so that if the reverse is OK, it would look normal. However, in many instances as you turn a coin over in your fingers, you just can not do it perfectly so a slight rotation goes unnoticed.
Of course a massive change in degrees would be noticed by many, but even then, not by most. And remember that probably 90% of the people in this country do not know that when you turn any US coin over from top to bottom, the reverse is now still right side up.

rotated die coins are more common than you would think. but to be of any value over face you will need to have 15% or more some say 10% will do it but in order to get a good price 15 is a good starting point. a 10% cent (lets say just as an example) would get maybe 2 cents if your lucky but a 15% would get maybe a nickel but when you get past 15 the price will grow about 10% per degree.
i hope that I made this understandable lol
Good Luck
Gary