Because if there is more than one login on the system, then that user, unprivileged can do this:
rm -rf /var/games/minecraft/servers/*
You’ve given _all users, no matter who you are, write access to each of the files (tamper with file) and the ability to delete the files. It’s poor security practice, even if security of a casual minecraft server is not the highest focus.
Also, here’s my own personal take on it: Need help with java crashing with SIGSEGV error - #4 by hexparrot