Wyrms, Forest Spirits, Pegasi, Fire Spirits, Lava Golems, and Graviton Fire Eaters are all widely used creatures that have active skills that can greatly increase their damage potential.
Lobotomizer can cripple these growth/ablaze/dive creatures by simply removing their skills.
Mono-aether doesn't necessarily use Phase Dragons; Phase Spiders are very cheap and are strong fighters. Lobotomizing Otyughs will protect your Spiders.
Also, Lobotomizer does not always have to work with Mono-Aether. Lobotomizer is great in many rainbow decks or duo decks, where it is still very useful.