Rent was the first show to switch to a lottery because people started camping out overnight and in the wee hours of the morning for the front row rush seats on a consistent basis. The producers and I believe even the city thought it was unsafe and that the policy needed to change. In still wanting to keep cheap tickets for the diehard fans, the lottery was born so that large crowds would amass for only a short period of time and there'd be no incentive to "camp out" and clog the sidewalks for hours.
Extremely popular shows that would potentially have people camp out to score rush tickets like Wicked, The Book of Mormon, and now Matilda have followed in Rent's footsteps. Since people were getting to the Shubert at 4 am and the problem would likely only get worse as summer picks up and after the Tonys, it seems the producers made a good call here.
Scratch and claw for every day you're worth!
Make them drag you screaming from life, keep dreaming
You'll live forever here on earth.