The point of a lottery is to raise money for the party running the lottery.
As such, the primary goal is to get people excited and wanting to buy more tickets.
It's been well proven that a lower chance at some astronomically huge number gets the class of folks who "invest" in lottery tickets to buy much more than a higher chance of a lower number.
Much like many stores found out people would actually pay more for something that has a 70% off clearance tag on it, than they would pay for the same item at at every day low price that was actually less than a "sale" price.