Why only twenty two?

I am new to the tarot cards, and I have a little question: why there are only twenty two cards? Is it possible to create my own system with different number of Major Arcanas? Have anyone tried creating more variable divination cards systems? If so, please reply in comments?

Ps: Asking just out of interest as I am a newbie to this art.

PPs: I know about Minor Arcana, I just had question if it is possible to create and add your own cards with new symbolism or creating your own Major Arcana.