Because it something that you want.
If you want challenge play untwinked without switching items. Or play without healing or something like that.
Mobs having more hp and slightly more damage is not challenge.
If you can play without players x, play offline where you can use it as you like.
Adding that command online would be poor decision as it is antisocial feature. It would give players more reasons to play solo.
They can help situation in different ways.