Shakespeare's plays considered difficult for modern students to
Why are
understand?

They are plays, which is to say, they are instructions to actors as to what to say in the performance of the play. They are best understood when they are watched, not when they are read. If you want to know what a movie is all about, do you read the screenplay, or do you watch the movie? Of course you watch it. The ability to read and understand playscripts requires an understanding of dramatic convention and a good imagination, and it is not easy, especially the first time. Unfortunately Shakespeare's plays are usually the first plays students read.

Explanation:

Shakespeare wrote using verse. Many of his characters speak in it. What this means is that there is a rhythm to their speech and sometimes Shakespeare bends the syntax to fit the rhythm. So, instead of having Richard III say "buried in the deep bosom of the ocean" he has him say "in the deep bosom of the ocean buried," moving the verb to the end of the sentence. Formerly, this was a common custom among people writing lyrics to songs, to make them fit the rhythm of the melody. More recently, however, lyricists do not try to match their lyrics to the melody; they alter the melody to match the lyric. As a result, English speakers these days have very rigid expectations of syntax and easily get confused when it is altered.