There are actually tons of varieties in modern coins. However, for some reason they just don'e get publicized. At one coin show I go to there is a guy that has binders full of those 20 pocket plastic pages of 2x2's. All are error or variety types. He has most denominations from the Cent up. They are all out there but for some reason just no popularity.
For example if you purchased that book called Looking Through Lincoln Cents by Charles Daughtrey you would see that there are errors and/or varieties for almost every year that those things have been made. Yet all people talk about is the 1955 Doubled Die as if it was the only one.
And so many people completely ignor rotated reverses. Great example is the famous
Red Book on pages 421 and up, lots of photos and stories about all the possible types of errors, yet no mention of rotated reverses. Possibly don't exist?

Then we have things like the 1974 Aluminum Cent. Is it real? Check your pockets. Just remember with coins it is a lot to do with popularity as to what to look for, what is out there, what was made.
There are lots and lots of varieties and errors. Just not publicized.