why do they amke two part movies instead of the whole thing.

They say that making two part movies is a good idea like when they made part on and part two of Harry Potter and part one and two of the Twilight Saga Breaking Dawn that which is stupid i saw part one of the Harry Potter movie it was good but still i can't believe they'd devided the movie into a two part movie as much as it was stupid coming up with a title of a stupid movie like "I am number Four" and "Indiana Jones kingdom of the cristal skull" i,m not going to go see "I am number Four" but i can't believe i wanted to go see "Indiana Jones" mixing indiana jones with alians? please that was really stupid i,m not seeing any movies like the movies that i,m talking about and i,m still not going to go see that movie "I am number Four" i will not.