Here are some of the problems with colonzing Mars, it would take trillions of dollars, it would be incredibly boring, who would actually want to live on Mars, you would need to take a massive amount of supplies with you (which includes oxygen, food, water, shelter, all the other supplies for other people too, and more), there is only a small window of time to go from Earth to Mars (and vice versa), the surface of Mars is a desert meaning that it can be -90 C (at the mid winter poles it drops to -200 C) at night and then 110 C in the day, there are no usable resources on the surface (examples: food, water, so bring even more supplies), there are sandstorms every day, AND the most important thing is that it is utterly pointless
Edit: I just clicked the poll results, 75% yes, WHAT IS WRONG WITH YOU PEOPLE?!