I am not sure the reason, it could have been a packging error under 6.1. The +s enables the setuid bit on the binary. This means the binary will be run as the owner of the binary (this case root) no matter who runs the binary. It is a dangerous thing to enable and the code you enable it on needs to be well trusted. But it is the only way to elivate a normal user to root without re-logging in.