People believe it's harmless fun.
Even if sometimes someone gets hurt seriously such news doesn't come out that much in the public domain (until and unless it's a matter of life or death).
During the second year of Engineering, we got some new classmates who had completed their diploma and all were from different colleges.
And few of them had seen some people getting seriously injured in their respective colleges so they abstained from such practices.
On the other hand, the other set of people hadn't seen someone getting seriously injured so the continued with such practices.