I know that some anti cheat features belong to plugins but I believe that Sponge should (as Spigot and Minecraft Vanilla did) implement some obvious anti cheat features.
This are related but not limited to:
Anti fly (as Minecraft Vanilla does kicking the user that is flying for more than x seconds)
Anti fastplace (as Spigot implemented once, limiting the number of blockplace packets per x seconds)
Anti fastbreak (as Spigot implemented once, limiting the number of blockbreak packets per x seconds)
Anti xray (Integrated into the server .jar improves performance (as Spigot does)).
Some anti dupe fixes (If a duplication bug appears, Sponge should be fast pached like Bukkit did one time).
I am not suggesting to implement a NoCheatPlus like plugin into Sponge, just the basic and easy checks like the ones I listed here.
Ya I’m against this, leave this up to server owners sponge shouldn’t try and handle anti-cheat because updating it will become a burden and we’ve already seen the community is more than willing to do this as a plugin.
I personally agree with @Iroh and @Garrison because I have known servers that randomly kicked players when they are just glitching. If they include anti-cheat then what is stopping them from adding things like economy, permissions, etc. like @IDragonfire said. If they add these things I feel it could be taking away from the survival aspect that some server owners want.