At its core DnD is a wargame where we spend most of the game time fighting against monsters and bad guys. Having robust combat systems is the big draw of the game and fighting monsters in interesting ways without being too unfair either way. People want rules that are robust enough to make interesting combat but don't completely break down under a bit of the box thinking, like the peasant rail gun, or the moon box lich, or the create water in someone's lungs to cause drowning, or the coffeelock to get infinite spell slots.

All of these mechanical oversights are frustrating to play with because we have to stop the game and debate over whether this cheesy game breaking bullshit should be allowed at the table and it takes time away from the reason we're all here, to get together play a game, and let everyone have fun, DM included. And sitting around debating whether the moon counts as a container for a lich's soul reliquary or lining up 500 peasants and each of them readying and handing off an object at a bazillion mph for an hour and a half breaks the rules is not fun.

You want a system for magic that encourages being busted even at high levels? Play some Mage the Ascension, you can do some absurdly wacky shit even at fairly low power levels.