Because is one of John Lennon's most compelling songs. The combination of melody, chord progression, vocal harmonies and arrangement is very creative and far beyond most composers, especially considering he was still not yet 30 years old.
This arrangement follows my CD from about 30 years ago, A Beatles Collection and starts with just the harpsichord accompaniment before bringing in the melody, which is played in two different octaves. There are some unorthodox fingerings, like using one finger to play two notes on different frets at the same time, but alternatives are also explored.
There are a lot of barre chords needed, which can make it very tiring, but it will be worth your time if you decide to tackle it.