There aren't enough cacti in the class. Therefore, cacti must be bought to fill the empty space within the class, and within our hearts. 

Pros:

Medicinal

Natural

Awe-inspiring

For defence against Intruders

Doesn't need much caring

Inspire creative thinking

Enhances environment

Cures depression

Doesn't cause cancer

Has never committed a crime

Not racist

Cons:

If your dumb enough to fall in that's on you; don't hate the player hate the game. I.e. no cons