Widespread cheating can lead to a "dead" server where new players feel unwelcome due to the insurmountable gap between hackers and legitimate users.
Most public Eaglercraft servers (like eaglercraft.org or lax1dude.net ) have active admins who use simple anti-cheat. A blatant Kill Aura gets you banned within 2 minutes. Furthermore, these servers often "shadow ban" by adding you to a lag machine, making you think the hack is broken.