You say lazy, I say efficient. All that text and metatext is already in the spell chapter so pointing a feature there makes a lot of sense.
Spells are also already benchmarked by class level in terms of relative power. It's not perfect by any means, but designers, players, and DMs can look at a feature that grants Nondetection and gauge whether that's truly worthwhile at 9th level when casters are getting it at 5th and half-casters at 7th, potentially multiple times per long rest even.